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Article

Cobalt Coordination Networks Based on the Linker (Phenazine-5,10-diyl)di- and Tetrabenzoate

by
Annette Vollrath
,
Xiang Liu
,
Nikolas Jansen
,
Philipp Seiffert
,
David Geller
and
Christoph Janiak
*
Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität, 40204 Düsseldorf, Germany
*
Author to whom correspondence should be addressed.
Crystals 2026, 16(3), 185; https://doi.org/10.3390/cryst16030185
Submission received: 15 January 2026 / Revised: 1 March 2026 / Accepted: 2 March 2026 / Published: 10 March 2026
(This article belongs to the Special Issue Synthesis, Crystal Structures and Hirshfeld Surface Analysis of Coordination Compounds (3rd Edition))
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Versions Notes

Abstract

The crystal structures of the cobalt(II) metal–organic frameworks or coordination networks of [Co(pdb)(DMF)] and [Co2(pdi)(DMF)3]·2(DMF)·H2O (H2pdb = 3,3′-(phenazine-5,10-diyl)dibenzoic acid; H4pdi = 5,5′-(phenazine-5,10-diyl)diisophthalic acid; DMF = N,N-dimethylformamide) were synthesized solvothermally from cobalt(II) nitrate and the free acid of the linker in DMF. Systematic solvothermal screening demonstrated strong metal- and counterion-dependent framework formation, as crystalline coordination polymers were obtained exclusively from cobalt(II) nitrate, whereas other metal salts and cobalt(II) chloride or sulfate produced no crystalline materials. In catena-[(N,N-dimethylformamide)-μ4-3,3′-(phenazine-5,10-diyl)dibenzoate-cobalt(II)], [Co(pdb)(DMF)], the Co2 units, acting as secondary building units, are coordinated by four carboxylate groups from four linkers in a paddle-wheel arrangement, giving a three-dimensional (3D) network with cds (or CdSO4) topology, in which the wide openings are filled by two symmetry-related nets to form a threefold interpenetrated structure. In catena-[tris(N,N-dimethylformamide)-μ8-5,5′-(phenazine-5,10-diyl)diisophthalate-dicobalt(II)] bis(N,N-dimethylformamide) hydrate, [Co2(pdi)(DMF)3]·2(DMF)·H2O, there are two different Co atoms, of which only Co2 is connected to each of the four carboxylate groups of the tetracarboxylate linker and, thus, is responsible for 3D network formation. The network topology in [Co2(pdi)(DMF)3] is pts (or platinum(II) sulfide) when taking the Co2 atom as a tetrahedral node and the linker as a square-planar fourfold node; however, this arrangement is inverse to the common square-planar metal and tetrahedral linker nodes found in PtS and most pts topologies.

1. Introduction

Incorporating redox-active carboxylate linkers—such as those based on phenazine—into the construction of new coordination polymers (CPs) and metal–organic frameworks (MOFs) offers expanded opportunities to harness redox behavior [1,2,3,4]. Phenazine derivatives contain a dibenzo-fused pyrazine core and are well known for their intrinsic redox activity. They can be readily reduced to 5,10-dihydrophenazines, which, together with subsequent transformations, give access to a wide range of dihydrophenazine derivatives (Scheme 1) [5]. Dihydrophenazines (DHPs), particularly N,N′-substituted diaryl-phenazin-5,10-diyls, are electron-rich species that generate stable radical cations upon irradiation, heating, electrochemical oxidation, or treatment with suitable chemical oxidants [6]. Owing to their pronounced redox activity and the stability of their radical cations [7,8], DHPs display distinctive optical, electronic, magnetic, and catalytic characteristics [9,10,11]. Several diaryl-substituted DHPs have been identified as effective photoredox catalysts for visible light-mediated atom transfer radical polymerization [12,13,14,15,16,17].
Dihydrophenazine-based organic polymers [9,10,18], MOFs [10,19,20] and coordination cages [21] have been investigated for their electrochemical behavior [22,23,24] and have been explored as heterogeneous catalysts. While previous publications have reported on phenazine-based covalent organic frameworks (COFs) used for catalytic and optoelectronic applications [25,26,27], DHP-containing 2D and 3D covalent organic frameworks have demonstrated high efficiency as heterogeneous photocatalysts for the radical ring-opening polymerization of vinylcyclopropanes [18]. UiO-type MOF [Zr6(μ3-O)4(μ3-OH)4(pzdb)6] (pzdb = 4,4′-(phenazine-5,10-diyl)dibenzoate)) [10] has been successfully utilized as a heterogeneous donor component to enhance catalytic electron donor–acceptor photoactivation. Similarly, the [Zn2(pzdb)2(dabco)]·4DMF (dabco = 1,4-diazabicyclo[2.2.2]octane) framework has been applied as a heterogeneous catalyst for aza-Diels–Alder reactions [28].
Recently, UV/Vis/NIR spectroelectrochemistry revealed that the pzdb linker is the primary redox site in coordination polymers [Zn(pzdb)(DEF)2] and [Co(Hpzdp)2(DEF)2] (DEF = N,N-diethylformamide) upon electrochemical oxidation or chemical oxidation with SbCl5 based on the same color changes as in Me2pzdb, together with EPR signals typical of ligand-based radical cations. However, the coordination polymers decomposed upon pzdb linker oxidation [29].
Here, we report the synthesis and characterization of two new coordination networks based on DHP-derived redox-active linkers H2pdb and H4pdi.

2. Materials and Methods

All chemicals were purchased from commercial suppliers and used without further purification (see Supplementary Material, Section S1 for details). Deionized water was employed in all procedures involving water using a Sartorius Arium Mini water purifier (Sartorius, Göttingen, Germany). Single-crystal X-ray diffraction data were collected on a Rigaku XtaLAB Synergy S instrument (Rigaku, Tokyo, Japan) equipped with a PhotonJet Cu Kα radiation source (λ = 1.54184 Å) and a hybrid pixel array detector. Suitable crystals were selected under a Leica M80 polarized-light microscope (Leica, Wetzlar, Germany) and mounted on a cryo-loop in oil. Data processing—including unit-cell refinement, data reduction, and absorption correction—was carried out with CrysAlisPro, version 171.42.102a. Structures were solved and refined in Olex2, version 1.5, using SHELXT and SHELXL, respectively [30,31,32]. Molecular graphics were generated using Diamond 5 software [33].
Powder X-ray diffraction (PXRD) data were collected at room temperature on a Rigaku Mini-Flex600 diffractometer (Rigaku, Tokyo, Japan) (600 W, 40 kV, 15 mA) using Cu Kα radiation (λ = 1.54184 Å). The samples were dried for 12 h at 60 °C under vacuum. PXRD patterns were normalized to the intensity of the most intense peak. Simulated PXRD patterns were obtained from MERCURY 2020.3.0 using the single-crystal XRD data [34].
Fourier transform infrared (FT-IR) spectra were recorded between 500 and 4000 cm−1 using a Bruker TENSOR 37 spectrometer (Bruker, Billerica, MA, USA) in ATR mode (Platinum ATR-QL, Diamond). Nuclear magnetic resonance (NMR) spectra were measured on a Bruker Avance III 300 spectrometer (Bruker, Billerica, MA, USA) operating at 300 MHz for 1H NMR and 150 MHz for 13C NMR. Electron impact (EI) mass spectra were obtained using a Thermo Finnigan Trace DSQ spectrometer (Thermo Fisher Scientific, Waltham, MA, USA).
N2 sorption measurements were carried out with a Belsorp Max II (Microtrac, MRB, Haan, Germany) volumetric gas sorption analyzer at 77 K. Samples were pre-dried for 12 h at 60 °C under vacuum, then activated at the sorption analyzer under turbomolecular pump vacuum (5 · 10−12 bar) for 3 h at 130 °C.
Thermogravimetric analysis (TGA) was carried out in air and under nitrogen on a Netzsch TG209 F3 Tarsus instrument (Netzsch, Selb, Germany) at a heating rate of 10 K min−1 up to 1000 °C. Gaseous products were analyzed with a GAM 200 mass spectrometer from InProcess Instruments (InProcess Instruments, Bremen, Germany). Melting points were measured in open capillaries using a Büchi Melting Point B-540 apparatus (Büchi Labortechnik AG, Flawil, Switzerland).
Elemental analyses were conducted on a PerkinElmer 2400 series II elemental analyzer (PerkinElmer, Waltham, MA, USA) (accuracy of 0.5%). The samples were dried at 180 °C under vacuum (10−3 bar).
Electrochemical experiments were performed using an Interfere 1010E potentiostat (Gamry Instruments, Warminster, PA, USA) coupled with an RRDE-3A system (ALS, Tokyo, Japan). Measurements were carried out in a three-electrode configuration, employing an Ag/AgCl reference electrode (stored in 3.5 mol L−1 KCl), a platinum counter electrode, and a glassy carbon working electrode with a diameter of 5 mm. The electrolyte consisted of nitrogen-purged acetonitrile containing 0.5 mol L−1 tetrabutylammonium hexafluorophosphate. The catalyst ink was prepared by dispersing 1 mg of the sample in a mixture of 0.25 mL of ethanol and 0.25 mL of water, followed by sonication for 30 min. Subsequently, 10 µL of the ink was drop-cast onto the working electrode and dried at 150 rpm, resulting in a catalyst loading of approximately 10 µg cm−2. Cyclic voltammetry measurements were conducted over a potential range of −0.7 V to 1.5 V versus Ag/AgCl at a scan rate of 100 mV s−1.

2.1. Synthesis of 5,10-Dihydrophenazine (Scheme S1)

Phenazine (4.00 g, 22.2 mmol) was dissolved in 50 mL of ethanol in a 500 mL round-bottom flask. Sodium dithionite (38.7 g, 222 mmol) was dissolved in 250 mL of deionized water. The two solutions were then combined in the flask, which was heated to 95 °C under stirring and reflux for 3 h. After the flask was cooled to room temperature. the reaction mixture was filtered, and the product was dried under vacuum for 40 min. Finally, the product was stored under a protective N2 atmosphere. Yield: 3.69 g (91%). 1H-NMR (300 MHz, DMSO-d6): δ [ppm] = 7.29 (s, 2 H), 6.25 (dd, J = 6.7, 3.4 Hz, 4 H), 6.01 (dd, J = 6.7, 3.5 Hz, 4 H).

2.2. Synthesis of Dimethyl-3,3′-(Phenazine-5,10-diyl)Dibenzoate (Me2pdb) (Scheme S2)

A 100 mL three-neck flask was charged with 1.00 g of 5,10-dihydrophenazine (5.50 mmol), 2.60 g of 3-methyl 3-bromobenzoate (12.1 mmol), and 1.52 g of potassium carbonate (16.5 mmol). After sealing the flask, a solution of 0.062 g of palladium(II)-acetate (0.27 mmol) and 0.3 mL of tri-tert-butylphosphine dissolved in 60 mL of xylene was added. The reaction mixture was heated under stirring to reflux for 48 h. After cooling to room temperature, 100 mL of water was added to the reaction mixture, and it was extracted with 3 × 150 mL of dichlormethane. The combined organic phases were washed with 150 mL of brine solution (60 g NaCl in 300 mL water) and were dried over magnesium sulfate. The organic solution was concentrated using a rotary evaporator. After adding 5 mL of DCM and 40 mL of n-hexane, the product was recrystallized in the refrigerator. The precipitate was filtered off and dried under vacuum. Yield: 1.83 g (74%). 1H-NMR (300 MHz, CDCl3): δ [ppm] = 8.20–8.08 (m, 4 H), 7.71 (t, J = 9.0, 6.0 Hz, 2 H), 7.65–7.59 (m, 4 H), 6.28 (dd, J = 6.7, 3.4 Hz, 4 H), 5.58 (dd, J = 6.7, 3.4 Hz, 4 H), 3.94 (s, 6 H). %). 13C{1H}-NMR (600 MHz, CDCl3): δ [ppm] = 166.16, 140.34, 136.31, 136.16, 133.73, 132.93, 131.51, 129.49, 121.13, 112.62, 52.36. [HR-ESI-MS] m/z = 450.16 (calculated for 12C28 1H22 14N2 16O4 450.16). IR (ATR): υ [cm−1] = 3430, 3076, 3037, 3006, 2953, 2841, 2625, 2579, 1911, 1719, 1660, 1629, 1609, 1596, 1580, 1484, 1440, 1391, 1347, 1287, 1261, 1192, 1173, 1158, 1129, 1098, 1078, 1062, 991, 949, 928, 889, 838, 813, 794, 733, 693, 678, 643, 618, 558. Mp. = 255 °C.

2.3. Synthesis of 3,3′-(Phenazine-5,10-diyl)Dibenzoic Acid (H2pdb) (Scheme S3)

A solution of 1.72 g (3.82 mmol) of dimethyl-3,3′-(phenazine-5,10-diyl)dibenzoate in 25 mL of 1,4-dioxane was prepared in a 100 mL flask. Then, 1.60 g of lithium hydroxide (38.2 mmol) and 15 mL of water were added to the reaction mixture, which was then heated to 100 °C for 24 h. After cooling to room temperature, the mixture was neutralized with concentrated hydrochloric acid (~1.9 mL). The precipitation was then filtered and dried under vacuum. Yield: 1.53 g (91%). 1H-NMR (300 MHz, DMSO-d6): δ [ppm] = 13.07 (s, 2 H), 8.08 (dt, 2 H), 7.92 (t, J = 9.0, 6.0 Hz, 2 H), 7.82 (t, J = 9.0, 6.0 Hz, 2 H), 7,73 (dt, 2 H), 6.30 (dd, J = 6.7, 3.4 Hz, 4 H), 5.52 (dd, J = 6.7, 3.4 Hz, 4 H). 13C{1H}-NMR (600 MHz, DMSO-d6): δ [ppm] = 166.47, 139.94, 135.75, 134.75, 134.74, 132.00, 131.70, 129.25, 121.19, 112.49. [HR-ESI-MS] m/z = 422.13 (calculated for 12C26 1H18 14N2 16O4 422.13). IR (ATR): υ [cm−1] = 3386, 3067, 2994, 2857, 2814, 2662, 2540, 1979, 1909, 1865, 1821, 1748, 1683, 1609, 1597, 1581, 1483, 1443, 1411, 1388, 1344, 1280, 1183, 1160, 1138, 1103, 1082, 1061, 1002, 990, 965, 928, 912, 838, 819, 757, 734, 693, 669, 643, 617, 568. Mp. > 350 °C.

2.4. Synthesis of Tetramethyl-5,5′-(Phenazine-5,10-diyl)Diisophthalate (Me4pdi) (Scheme S4)

A 100 mL three-neck flask was charged with 1.00 g of 5,10-dihydrophenazine (5.50 mmol), 2.60 g of dimethyl-5-bromoisophthalate (12.1 mmol), and 1.52 g of potassium carbonate (16.5 mmol). After sealing the flask, a solution of 0.062 g of palladium(II)-acetate (0.27 mmol) and 0.3 mL of tri-tert-butylphosphine dissolved in 60 mL of xylene was added. The reaction mixture was heated under stirring to reflux for 48 h. After cooling to room temperature, 100 mL of water was added to the reaction mixture, and it was extracted with 3 × 150 mL of dichlormethane. The combined organic phases were washed with 150 mL of brine solution (60 g NaCl in 300 mL water) and were dried over magnesium sulfate. The organic solution was concentrated using a rotary evaporator. After adding 5 mL of DCM and 40 mL of n-hexane, the product was recrystallized in a refrigerator. The precipitate was filtered off and dried under vacuum. Yield: 2.12 g (68%). 1H-NMR (300 MHz, CDCl3): δ [ppm] = 8.80 (t, J = 3.0, 3.0 Hz, 2 H), 8.32 (d, 4 H), 6.32 (dd, J = 6.7, 3.4 Hz, 4 H), 5.59 (dd, J = 6.7, 3.4 Hz, 4 H), 3.98 (s, 12 H). 13C{1H}-NMR (600 MHz, CDCl3): δ [ppm] = 165.47, 141.00, 137.72, 135.96, 134.35, 130.68, 121.66, 113.12, 52.79. [HR-ESI-MS] m/z = 566.17 (calculated for 12C32 1H26 14N2 16O8 566.17). IR (ATR): υ [cm−1] = 3431, 3088, 3004, 2954, 2846, 1718, 1590, 1544, 1489, 1434, 1398, 1355, 1307, 1287, 1242, 1199, 1167, 1137, 1105, 1065, 998, 950, 938, 918, 898, 876, 834, 806, 784, 753, 741, 723, 686, 664, 618, 562. Mp. = 336 °C.

2.5. Synthesis of 5,5′-(Phenazine-5,10-diyl)Diisophthalic Acid (H4pdi) (Scheme S5)

A solution of 1.00 g (1.77 mmol) of tetramethyl-5,5′-(phenazine-5,10-diyl)diisophthalate in 25 mL of 1,4-dioxane was prepared in a 100 mL flask. Then, 0.74 g of lithium hydroxide (17.7 mmol) and 15 mL of water were added to the reaction mixture, which was heated to 100 °C for 24 h. After cooling to room temperature, the mixture was neutralized with concentrated hydrochloric acid (~1.5 mL). The precipitation was then filtered and dried under vacuum. Yield: 0.71 g (79%). 1H-NMR (300 MHz, D2O): δ [ppm] = 8.33 (t, J = 3.0, 3.0 Hz, 2 H), 7.89 (d, 4 H), 6.30 (dd, J = 6.7, 3.4 Hz, 4 H), 5.67 (dd, J = 6.7, 3.4 Hz, 4 H). 13C{1H}-NMR (600 MHz, D2O): δ [ppm] = 174.03, 140.06, 139.67, 136.08, 134.08, 128.94, 121.48, 113.00. IR (ATR): υ [cm−1] = 3384, 3079, 3063, 2981, 2861, 2824, 2665, 2616, 2572, 2540, 1891, 1865, 1723, 1694, 1635, 1591, 1552, 1488, 1455, 1423, 1351, 1311, 1279, 1244, 1192, 1159, 1109, 1064, 1003, 957, 925, 847, 790, 756, 729, 693, 681, 661, 615, 602. Mp. > 350 °C.

2.6. Synthesis of Catena-[(N,N-Dimethylformamide)-μ4-3,3′-(Phenazine-5,10-diyl)Dibenzoate-Cobalt(II)], [Co(pdb)(DMF)]

First, 15.0 mg of H2pdb (0.034 mmol) and 20.0 mg of cobalt nitrate hexahydrate (0.068 mmol) were placed in a glass tube. Then, 2 mL of DMF was added to completely dissolve the solids. The tubes were sealed and placed in an oven at 100 °C for two days. Dark-red crystals were obtained as a final product. The crystals were washed with DMF and ethanol and dried under vacuum. Yield: 11 mg (56%). C29H23CoN3O5 ([Co(pdb)(DMF)]): calc. C C 63.04, H 4.20, N 7.61%; exp. C 62.14, H 4.23, N 7.76%.
MOFs and coordination networks cannot be purified by recrystallization as molecular compounds can. Importantly, varying degrees of missing linker or missing cluster defects lead to deviations from the ideal formula, which cannot be alleviated. A missing anionic linker cannot only be replaced by coordinated solvent but also needs hydroxide or anionic ligands from the metal salt precursor for charge compensation. Furthermore, a difficult-to-control loss of crystal or coordinating solvent molecules and possible hydration upon sample handling in air can also occur. Therefore, elemental analyses are often not reported for MOFs because of the known mismatch. Crystal-phase purity is usually established by matching the experimental and simulated PXRD.

2.7. Synthesis of Catena-[tris(N,N-Dimethylformamide)-μ8-5,5′-(Phenazine-5,10-diyl)Diisophthalate-Dicobalt(II)] bis(N,N-Dimethylformamide) Hydrate [Co2(pdi)(DMF)3]·2(DMF)·H2O

First, 17.9 mg of H4pdi (0.035 mmol) and 20 mg of cobalt nitrate hexahydrate (0.070 mmol) were placed in a glass tube. Then, 2 mL of DMF was added to completely dissolve the solids. The tubes were sealed and placed in an oven at 100 °C for two days. Dark-red crystals were obtained as a final product. The crystals were washed with DMF and ethanol and dried under vacuum. Yield: 22 mg (62%). C43H51Co2N7O14 ([Co2(pdi)(DMF)3]·2(DMF)·H2O): calc. C C 51.24, H 5.10, N 9.73%; exp. C 48.56, H 3.58, N 6.73%. We note that for porous MOFs, the solvent content in the pores can change during sample handling, often leading to deviating elemental analyses (see also the comment on CHN analysis in Section 2.6).

3. Results and Discussion

The syntheses of the linkers started with the reduction of phenazine with sodium dithionate to 5,10-dihydrophenazine (DHP, Scheme 1, Scheme S1) [1]. DHP is a light-green solid and was stored under a nitrogen atmosphere because of its easy re-oxidation in air. 1H NMR spectroscopy (Figure S1) confirmed the product with high purity. In the next reaction step, dimethyl-3,3′-(phenazine-5,10-diyl)dibenzoate [3,3′-(phenazine-5,10-diyl)dibenzoate dimethyl ester] or tetramethyl-5,5′-(phenazine-5,10-diyl)diisophthalate was synthesized (Schemes S2 or S4) through Buchwald–Hartwig coupling [19,35,36]. The highest yields and purest products were obtained with palladium(II) acetate as the catalyst, tri-tert-butylphosphine as the ligand and potassium carbonate as the base. The products are yellow or red powders, and their constitution and high purity are confirmed by NMR spectroscopy (Figures S2–S5).
Finally, the methyl esters were hydrolyzed with LiOH in a 1,4-dioxane/H2O mixture to give 3,3′-(phenazine-5,10-diyl)dibenzoic acid as a light-yellow solid (H2pdb, Scheme S3) or 5,5′-(phenazine-5,10-diyl)diisophthalic acid as a dark-green solid (H4pdi, Scheme S5). Again the 1H-NMR spectra are consistent with the constitutions (Figures S6–S9). The bands in the infrared spectra of the esters and the free acids can be assigned (Figures S10 and S11).
Various futile synthesis attempts were performed with zirconium(IV) chloride, zirconium oxychloride octahydrate, aluminum chloride hexahydrate, copper(II) chloride monohydrate, nickel(II) sulfate hexahydrate and nickel(II) chloride hexahydrate, with H2pdb and H4pdi in N,N-dimethylformamide giving no or no crystalline products. This was evident from the fact that either no reflections were visible in the measured PXRD (amorphous solid) or the same reflections as the pure linker were visible. Needle-shaped crystals from zinc nitrate hexahydrate with H2pdb in a molar ratio of 1:3 at 120 °C after two days were too small for single-crystal X-ray diffractometry. Good-quality crystals were obtained only in the reactions of cobalt(II) nitrate hexahydrate with H2pdb and H4pdi (both with a 2:1 molar ratio at 100 °C) after two days (Figures S12 and S13). The anion plays a certain role, as identical reactions of cobalt(II) sulfate heptahydrate and cobalt(II) chloride hexahydrate yielded no solid products.
The experimental powder X-ray diffraction patterns of the bulk crystallized cobalt compounds matched well with the simulated patterns derived from the crystal structures of [Co(pdb)(DMF)] and [Co2(pdi)(DMF)3]·2(DMF)·H2O, confirming their phase purity (Section S5, Figures S15 and S16).

3.1. Crystal Structures of [Co(pdb)(DMF)]

Figure 1 shows the extended asymmetric unit and cobalt coordination environment of [Co(pdb)(DMF)], and Table 1 lists the crystallographic data. The space group of this compound is I2/a. It belongs to the monoclinic crystal system, and the asymmetric unit consists of one cobalt(II) ion, two half pdb linkers and a DMF ligand. The pdb linker with N1 has a twofold rotation axis passing through the phenazine core perpendicular to the ring plane. The linker with N3 has an inversion center at the centroid of the phenazine ring. The cobalt(II) ion is square-pyramidally surrounded by five oxygen atoms and forms a Co2 handle as the secondary building unit (SBU) with another symmetry-equivalent cobalt(II) ion. This Co2 handle is surrounded by four carboxylate groups from four linkers in a paddle-wheel arrangement. Each pdb ligand acts as a tetradentate bridging ligand and connects two Co2 handles, being thereby bound to four cobalt atoms. The axial directions of the paddle-wheel unit bind to the oxygen atoms of the monodentate DMF ligands.
The selected bond lengths and bond angles can be found in Table 2. The bond lengths of the four cobalt–oxygen bonds in the equatorial plane range from 2.00 Å to 2.09 Å, and the bond length of the cobalt–oxygen(DMF) bond in the axial direction is approximately 2.03 Å. The cobalt–cobalt distance in the Co2 handle is 2.81 Å. The O-Co-O bond angles between the cis-positioned O atoms of the pdb linkers in the paddle-wheel unit are all approximately 90°, while the trans-O-Co-O angles are significantly smaller (~164°) because the Co···Co separation (2.81 Å) is larger than the O···O separation (~2.23 Å) in a carboxyl group so that the Co atom is placed “above” the equatorial plane of the four oxygen atoms. Consequently, the O-Co-O5(DMF) bond angle is also significantly greater than 90°. There is no significant π–π interaction and only limited C-H···π and C–H···O interactions in the supramolecular packing of the adjacent networks in [Co(pdb)(DMF)] (see Section S9 for details).
The Co2 handles or SBUs are then linked into a three-dimensional network with cds topology (Figure 2). In cds (or CdSO4) topology [37,38,39,40], each SBU is connected to four neighboring nodes via the linkers. If one starts with the chain shown in Figure 2a, where alternatingly, each SBU connects to a parallel chain from top to bottom and front to back, then the 3D network in Figure 2b is obtained.
The single network has wide openings that are several Ångströms across (Figure S13), even taking into account the space-filling van der Waals surface (Figure 2c). These openings are filled with two symmetry-related nets through interpenetration, giving a threefold interpenetrated structure with cds topology (Figure 3). Consequently, no voids remain, and there is no porosity in the network. A threefold interpenetrated cds topology was described in 3D-[Co(pam)(bpa)(H2O)2]·DMF (H2pam = pamoic acid, bpa = 1,2-di(4-pyridyl)ethylene, DMF = N,N-dimethylformamide) [41], and twofold interpenetrated cds net topologies were found in [Zn2(BDC)(BPP)Cl2] (BDC = benzene-1,4-dicarboxylate, BPP = 1,3-bis(4-pyridyl)propane) [42] and in [Cu(ceb)(bpmp)]·H2O (ceb = 4-(carboxylatoethyl)benzoato, bpmp = 1,4-bis(pyridin-4-ylmethyl)piperazine) [43]. Further examples of interpenetrated networks with a cds topology are [Zn(Br-1,3-bdc)(NI-mbpy-34)] (Br-1,3-bdc = 5-bromobenzene-1,3-dicarboxylate, NI-mbpy-34 = N-(pyridin-3-ylmethyl)-4-(pyridin-4-yl)-1,8-naphthalimide) [44] and [M(μ-TBG)(μ-H2O)(H2O)2]·2H2O (M = Cu, Co and H2TBG = terephthaloylbisglycine) [45]. A non-interpenetrated 3D network with cds topology was reported for [trans-Ni(H2O)2(μ-4,4′-bpy)2](ClO4)2 (4,4′-bpy = 4,4′-bipyridine) [46].
The combined TGA-DTG curve of [Co(pdb)(DMF)] is shown in Figure S18, and the TG-MS (TGA coupled with mass spectrometry) measurement is shown in Figure S20. The sample was pre-dried for 14 h at 180 °C under vacuum, cooled down under vacuum and rapidly transferred to the TGA instrument. There is no detectable mass loss below approximately 300 °C. The first mass-loss event of about 13 wt% is evident in the DTG at 360 °C and assigned to the removal of the DMF ligand (theor. 13 wt%) The solvent removal transits into the network decomposition of [Co(pdb)] without a clear plateau, and the sample is completely decomposed at ~430 °C with a concomitant mass loss of 73 wt% (theor. 76 wt%), as corroborated by the pronounced DTG minimum at around 410 °C. The final residue remains unchanged at approximately 14–15 wt%, consistent with the formation of cobalt oxide (CoO; theor. 14 wt% for CoO, 15 wt% for Co2O3, and 11 wt% for Co).

3.2. Crystal Structure of [Co2(pdi)(DMF)3]·2(DMF)·H2O

Figure 4 depicts the extended asymmetric unit and cobalt coordination environment of [Co2(pdi)(DMF)3]·2(DMF)·H2O, and Table 1 gives the crystallographic data. The space group of this compound is Pna21 in the orthorhombic crystal system. The asymmetric unit contains two crystallographically different cobalt(II) ions, a full pdi linker, three coordinated DMF ligands, two non-coordinated DMF molecules and a water molecule of solvation. Both cobalt(II) ions are sixfold coordinated and surrounded by six oxygen atoms, and they, again, form a Co2 handle as the secondary building unit. The Co1 ion is coordinated by the three DMF ligands and three carboxyl oxygen atoms of three different linkers in the facial configuration. Co2 is coordinated by four different pdi linkers, with two of them chelating and two monodentate. Each of the bridging linkers is connected to Co2, which can be seen as the primary metal node. Out of the four different carboxyl groups of the linker, two are monodentate bridging (O1-C-O2, O3-C-O4) between the two Co ions; one is bidentate bridging between Co1 and Co2 and, at the same time, chelating to Co2 (O5-C-O6 as κO:κO,κO’); and the last one is bidentate chelating to Co2 (O7-C-O8). From the perspective of the linker, each pdi ligand is bound to seven cobalt atoms, i.e., acts as a heptadentate-bridging ligand and connects four Co2 handles. Three handles are connected to both cobalt atoms—one handle only through one Co atom. Selected bond lengths and angles are listed in Table 3.
In [Co2(pdi)(DMF)3]·2(DMF)·H2O, crystal water and non-coordinated DMF solvent molecules are incorporated by hydrogen bonds in the crystal lattice. The hydrogen bonds of the crystal water molecule are shown in Figure 5. Hydrogen bond O14–H14A∙∙∙O8ii is between the water molecule and a cobalt-coordinating carboxyl oxygen atom of the pdi linker, and hydrogen bond O14–H14B∙∙∙O13ii is a bridge to a non-coordinated DMF molecule. These two hydrogen bonds are of medium strength, as the distance between the hydrogen atom and the accepting oxygen atom is between 1.9 and 2.0 Å in both cases. There is no π–π interaction—only C-H···π interactions originating from a coordinated DMF molecule in the packing of [Co2(pdi)(DMF)3]·2(DMF)·H2O. Also, the C–H···O interactions are largely between DMF molecules or from a coordinated DMF-CHO group to a cis-O atom of a carboxylate group. The water molecule accepts C-H bonds from DMF-CH3 and a diisophthalate-CH (see Section S9 for details).
The Co-pdi bridging action gives rise to a three-dimensional network (Figure 6). In this metal–ligand 3D network, there would be open channels (Figure 6a), which are, however, occupied by the coordinated DMF ligands, together with the DMF and H2O solvent molecules of crystallization (Figure 6b). When the free solvent molecules are omitted in the network, only small voids remain (Figure 7).
After activation, no N2 gas uptake could be detected with a volumetric gas sorption analyzer; hence, there is no N2 accessible porosity in the [Co2(pdi)(DMF)3] network. In view of the tight framework packing, the removal of the free DMF was probably not fully achieved, the framework partially collapsed and the potential voids were too small. For sorption measurement, the samples were pre-dried for 12 h at 60 °C under vacuum, then activated at the sorption analyzer under turbomolecular pump vacuum (5 · 10−12 bar) for 3 h at 130 °C, as stated in Section 2. The PXRD of the activated [Co2(pdi)(DMF)3]·2(DMF)·H2O sample shown in Figure S16 indicates that under these conditions, the sample turned amorphous, losing its defined pore structure.
The network topology in [Co2(pdi)(DMF)3] is pts (or platinum(II) sulfide) [37,47,48,49] when taking the Co2 atom as a tetrahedral and the linker as a square–planar fourfold node (Figure 6c). Among the two Co atoms, only Co2 is connected to each of the four carboxyl groups of the linker and is responsible for 3D network formation. Compared to the PtS structure, which is composed of square–planar Pt(II) and tetrahedral sulfide atoms, the pts topology in [Co2(pdi)(DMF)3] is reversed such that the metal node is tetrahedral and the linker square–planar.
For thermogravimetric analysis, the sample was pre-dried for 14 h at 180 °C under vacuum, cooled down under vacuum and rapidly transferred to the TGA instrument. The crystal solvent molecules water and DMF were removed under these conditions. The combined TGA–DTG curve (Figure S19) shows the first mass loss at ~300 °C due to the loss of the coordinated DMF (theor. 26 wt%). Without a pronounced plateau, the mass loss continues to ~390 °C with degradation of the organic linker (theor. 60 wt%). At 1000 °C, a residue of 21 wt% remains (theor. 18 wt% for CoO, 20 wt% for Co2O3, and 14 wt% for Co).
A comparison of the coordination polymer [Co(pdb)(DMF)] with the structurally related coordination polymers derived from isomeric dihydrophenazine-based dicarboxylate ligand H2PZDB (Figure 8) [29] highlights the combined influence of metal coordination preferences and ligand geometry on framework assembly. Although the two ligands share the same dihydrophenazine core, the relative orientation of the carboxylate groups differs between the meta and para positions, resulting in different coordination modes and network topologies. In the zinc and cobalt(II) coordination polymers based on H2PZDB [29], the axial or linear para-arrangement of the carboxylate functions favors extended but less densely interconnected networks, which predominantly adopt lower-dimensional architectures. In contrast, the pdb ligand employed in this work enforces a more angular coordination geometry through the meta-positions of the carboxylate groups, enabling tetradentate binding to dinuclear cobalt paddle-wheel units, and promotes the formation of a fully three-dimensional cds net with pronounced interpenetration.
Cyclovoltammetric (CV) studies were performed to investigate the redox behavior of phenazine-containing cobalt coordination compounds. However, [Co(pdb)(DMF)] exhibits only limited electrochemical stability under the applied conditions, as evidenced by the progressive changes in the cyclovoltammograms upon repeated cycling. In particular, continuous decrease and distortion of the redox features are observed (Figure S27a), indicating irreversible processes and/or decomposition of the electroactive species. For [Co2(pdi)(DMF)3]·2(DMF)·H2O, no well-defined redox waves could be obtained within the accessible potential window (Figure S27b). The recorded currents are largely featureless and dominated by background processes, suggesting that the redox events of the compound are either electrochemically irreversible or masked by concurrent chemical reactions. Consequently, CV measurements were not further used for quantitative analysis of the redox properties but are provided here only to document the observed behavior.

4. Conclusions

Two cobalt(II) coordination networks based on dihydrophenazine-derived dicarboxylate and tetracarboxylate linkers H2pdb and H4pdi were synthesized solvothermally and structurally characterized. Crystalline products were obtained only with cobalt(II) nitrate, highlighting the sensitivity of framework formation to the metal ion and its counterion when using rigid, multitopic carboxylate linkers. Systematic solvothermal reactions with other metal salts (Zr(IV), Al(III), Cu(II), Ni(II), and Zn(II)) under comparable conditions resulted in no or non-crystalline products. Only cobalt(II) nitrate yielded single crystals suitable for X-ray diffraction; notably, analogous reactions with cobalt(II) sulfate or chloride were unsuccessful, indicating a pronounced counterion effect.
In [Co(pdb)(DMF)], dinuclear cobalt paddle-wheel units are linked by tetradentate pdb ligands into a three-dimensional cds net that exhibits threefold interpenetration and results in a densely packed framework. In contrast, [Co2(pdi)(DMF)3]·2(DMF)·H2O contains two crystallographically distinct cobalt(II) centers, of which only one propagates the three-dimensional network, giving rise to an inverse pts topology with tetrahedral metal nodes and square–planar linker nodes.
These compounds demonstrate how the connectivity and geometry of dihydrophenazine-based carboxylate ligands govern the formation of secondary building units, network topology, and interpenetration in cobalt coordination polymers.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/cryst16030185/s1, Section S1: Chemicals used; Section S2: Reaction schemes for ligand syntheses; Section S3: NMR spectra; Section S4: IR spectra; Section S5: Overview of the conducted studies; Section S6: Crystal photographs and crystal structure images; Section S7: PXRD; Section S8: Thermogravimetric analyses; Section S9: Supramolecular analyses; Section S10: Electrochemical measurements. References [20,50,51,52,53,54,55] are cited in the Supplementary Materials.

Author Contributions

Conceptualization, A.V. and C.J.; methodology, A.V.; software, A.V.; validation, A.V., X.L. and N.J.; formal analysis, A.V., X.L., N.J., P.S. and D.G.; investigation, A.V., X.L., N.J., P.S. and D.G.; resources, C.J.; data curation, A.V., X.L. and N.J.; writing—original draft preparation, A.V. and C.J.; writing—review and editing, A.V. and C.J.; visualization, A.V. and C.J.; supervision, C.J.; project administration, C.J.; funding acquisition, C.J. All authors have read and agreed to the published version of the manuscript.

Funding

Funding was provided by the Deutsche Forschungsgemeinschaft (DFG) under grant 440366605 (for the Rigaku diffractometer). This work was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—396890929/GRK 2482.

Data Availability Statement

The data presented in this study are available upon request from the corresponding author. The CCDC numbers 2522790–2522791 for compounds [Co(pdb)(DMF)] and [Co2(pdi)(DMF)3]·2(DMF)·H2O, respectively, contain the supplementary crystallographic data reported in this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Center via www.ccdc.cam.ac.uk/data_request/cif (accessed on 14 January 2026).

Acknowledgments

The authors would like to thank Birgit Tommes for providing the IR measurements. We also thank the Center for Molecular and Structural Analytics at Heinrich Heine University (CeMSA@HHU) for recording the mass spectrometric and NMR spectrometric data.

Conflicts of Interest

The authors declare no conflicts of interest.

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Crystals 16 00185 sch001
Scheme 1. Synthesis route to the free acids of the H2pdb = 3,3′-(phenazine-5,10-diyl)dibenzoic acid (black skeletons) and H4pdi = 5,5′-(phenazine-5,10-diyl)diisophthalic acid (black plus pink structure parts; the attached methylcarboxyl and carboxyl groups in pink are only present in the Me4pdi and H4pdi compounds). For details, see Section 2 and Section S2 in the Supplementary Materials.
Scheme 1. Synthesis route to the free acids of the H2pdb = 3,3′-(phenazine-5,10-diyl)dibenzoic acid (black skeletons) and H4pdi = 5,5′-(phenazine-5,10-diyl)diisophthalic acid (black plus pink structure parts; the attached methylcarboxyl and carboxyl groups in pink are only present in the Me4pdi and H4pdi compounds). For details, see Section 2 and Section S2 in the Supplementary Materials.
Crystals 16 00185 sch001
Crystals 16 00185 g001
Figure 1. Expanded asymmetric unit for [Co(pdb)(DMF)]. Symmetry code: (i) −x + 1/2, −y + 3/2, −z + 3/2; (ii) −x + 3/2, y, −z + 1; (iii) −x, −y + 1, −z + 1 (50% thermal ellipsoids). Hydrogen atoms are not shown for clarity.
Figure 1. Expanded asymmetric unit for [Co(pdb)(DMF)]. Symmetry code: (i) −x + 1/2, −y + 3/2, −z + 3/2; (ii) −x + 3/2, y, −z + 1; (iii) −x, −y + 1, −z + 1 (50% thermal ellipsoids). Hydrogen atoms are not shown for clarity.
Crystals 16 00185 g001
Crystals 16 00185 g002aCrystals 16 00185 g002b
Figure 2. (a) Chain section of the 3D network in [Co(pdb)(DMF)], which is linked to parallel chains from top to bottom and front to back to give the full 3D network in (b) with cds topology. Hydrogen atoms are not shown for clarity, and the Co coordination is presented as polyhedra. (c) Space-filling view of the network with hydrogen atoms included.
Figure 2. (a) Chain section of the 3D network in [Co(pdb)(DMF)], which is linked to parallel chains from top to bottom and front to back to give the full 3D network in (b) with cds topology. Hydrogen atoms are not shown for clarity, and the Co coordination is presented as polyhedra. (c) Space-filling view of the network with hydrogen atoms included.
Crystals 16 00185 g002aCrystals 16 00185 g002b
Crystals 16 00185 g003aCrystals 16 00185 g003b
Figure 3. (a) The threefold interpenetrated structure of [Co(pdb)(DMF)]. Each network is shown in a different color. (b) Schematic representation of the threefold interpenetrated cds net in [Co(pdb)(DMF)], taking the midpoint of the Co2 handle as a fourfold node. The rods connect the Co2 midpoints and the phenazine-ring nitrogen atoms.
Figure 3. (a) The threefold interpenetrated structure of [Co(pdb)(DMF)]. Each network is shown in a different color. (b) Schematic representation of the threefold interpenetrated cds net in [Co(pdb)(DMF)], taking the midpoint of the Co2 handle as a fourfold node. The rods connect the Co2 midpoints and the phenazine-ring nitrogen atoms.
Crystals 16 00185 g003aCrystals 16 00185 g003b
Crystals 16 00185 g004
Figure 4. Expanded asymmetric unit for [Co2(pdi)(DMF)3]·2(DMF)·H2O. Symmetry code: (i) −x + 1/2, −y + 3/2, −z + 3/2; (ii) −x + 3/2, y, −z + 1; (iii) −x, −y + 1, −z + 1 (50% thermal ellipsoids). Hydrogen atoms are not shown for clarity.
Figure 4. Expanded asymmetric unit for [Co2(pdi)(DMF)3]·2(DMF)·H2O. Symmetry code: (i) −x + 1/2, −y + 3/2, −z + 3/2; (ii) −x + 3/2, y, −z + 1; (iii) −x, −y + 1, −z + 1 (50% thermal ellipsoids). Hydrogen atoms are not shown for clarity.
Crystals 16 00185 g004
Crystals 16 00185 g005
Figure 5. Hydrogen bonds (orange dotted lines) from the crystal water molecule in [Co2(pdi)(DMF)3]·2(DMF)·H2O.
Figure 5. Hydrogen bonds (orange dotted lines) from the crystal water molecule in [Co2(pdi)(DMF)3]·2(DMF)·H2O.
Crystals 16 00185 g005
Crystals 16 00185 g006aCrystals 16 00185 g006b
Figure 6. 3D network of [Co2(pdi)(DMF)3]·2(DMF)·H2O. (a) Hydrogen atoms, all DMF molecules and H2O molecules are omitted for clarity. (b) Hydrogen atoms, all DMF molecules and H2O molecules are shown within the unit cell. (c) Schematic representation of the pts net in [Co2(pdi)(DMF)3], taking the Co2 atom and the linker as fourfold nodes. The rods connect the Co2 atom and the midpoint of the phenazine-ring nitrogen atoms.
Figure 6. 3D network of [Co2(pdi)(DMF)3]·2(DMF)·H2O. (a) Hydrogen atoms, all DMF molecules and H2O molecules are omitted for clarity. (b) Hydrogen atoms, all DMF molecules and H2O molecules are shown within the unit cell. (c) Schematic representation of the pts net in [Co2(pdi)(DMF)3], taking the Co2 atom and the linker as fourfold nodes. The rods connect the Co2 atom and the midpoint of the phenazine-ring nitrogen atoms.
Crystals 16 00185 g006aCrystals 16 00185 g006b
Crystals 16 00185 g007
Figure 7. Space-filling view of the network [Co2(pdi)(DMF)3] with the coordinated DMF ligands to illustrate remaining small voids when the DMF and H2O solvent of crystallization were omitted (Co = cyan, O = red, N = blue, C = grey, H = white).
Figure 7. Space-filling view of the network [Co2(pdi)(DMF)3] with the coordinated DMF ligands to illustrate remaining small voids when the DMF and H2O solvent of crystallization were omitted (Co = cyan, O = red, N = blue, C = grey, H = white).
Crystals 16 00185 g007
Crystals 16 00185 g008
Figure 8. Simplified structural comparison of dihydrophenazine-based coordination polymers, highlighting the influence of ligand geometry and metal coordination on network topology. Coordination polymers based on isomeric dicarboxylate ligand H2PZDB (left and center; adapted from Reference [29]) form less densely interconnected architectures, whereas the cobalt(II) coordination polymer [Co(pdb)(DMF)] reported in this work (right) adopts a three-dimensional, highly interpenetrated framework. The comparison illustrates how subtle changes in carboxylate connectivity, in combination with the coordination flexibility of cobalt(II), govern framework dimensionality and packing.
Figure 8. Simplified structural comparison of dihydrophenazine-based coordination polymers, highlighting the influence of ligand geometry and metal coordination on network topology. Coordination polymers based on isomeric dicarboxylate ligand H2PZDB (left and center; adapted from Reference [29]) form less densely interconnected architectures, whereas the cobalt(II) coordination polymer [Co(pdb)(DMF)] reported in this work (right) adopts a three-dimensional, highly interpenetrated framework. The comparison illustrates how subtle changes in carboxylate connectivity, in combination with the coordination flexibility of cobalt(II), govern framework dimensionality and packing.
Crystals 16 00185 g008
Table 1. Crystal data for [Co(pdb)(DMF)] and [Co2(pdi)(DMF)3]·2(DMF)·H2O.
Table 1. Crystal data for [Co(pdb)(DMF)] and [Co2(pdi)(DMF)3]·2(DMF)·H2O.
[Co(pdb)(DMF)][Co2(pdi)(DMF)3]·2(DMF)·H2O
empirical formulaC29H23CoN3O5C43H51Co2N7O14
mol wt (g mol−1)552.431007.76
temperature (K)150150
crystal systemmonoclinicorthorhombic
space groupI2/aPna21
a (Å)9.5099 (6)26.9491 (5)
b (Å)18.7609 (15)15.5325 (3)
c (Å)27.3129 (19)11.4627 (2)
α (deg)9090
β (deg)91.587 (6)90
γ (deg)9090
volume, V (Å3)4871.1 (6)4798.14 (15)
Z, Z′8, 14, 1
Dcalc (g/cm3)1.5071.395
μ (mm−1)5.9226.02
F(000)22802096
crystal size [mm3]0.09 × 0.05 × 0.040.1 × 0.07 × 0.05
wavelength (Å)1.541841.54184
No. of unique reflections48408579
No. of total reflections27,26664,849
No. of parameters349608
Rint0.12680.0715
R[F2 > 2σ(F2)] (a)0.06320.0445
wR[F2 > 2σ(F2)] (a)0.12700.1091
R, wR(F2) [all data] (a)0.1248, 0.15230.0494, 0.1116
S [all data] (a)1.0731.041
Δρmax, Δρmin (e·Å−3) (b)0.678, −0.4710.722, −0.365
CCDC No.25227902522791
(a) R = [Σ(||Fo| − |Fc||)/Σ|Fo|]; wR = [Σ[w(Fo2 − Fc2)2]/Σ[w(Fo2)2]]1/2. Goodness-of-fit S = [Σ[w(Fo2 − Fc2)2]/(n − p)]1/2. (b) Largest difference peak and hole.
Table 2. Selected bond lengths (Å) and angles (°) for [Co(pdb)(DMF)] (a).
Table 2. Selected bond lengths (Å) and angles (°) for [Co(pdb)(DMF)] (a).
InteractionBond Length [Å]InteractionAngle [°]
Co1—O12.006 (4)O1—Co1—O598.90 (15)
Co1—O2 i2.023 (4)O1—Co1—O2 i163.69 (16)
Co1—O32.023 (3)O2 i—Co1—O4 i89.53 (15)
Co1—O4 i2.081 (3)O2 i—Co1—O597.18 (15)
Co1—O52.027 (3)O3—Co1—O4 i163.52 (13)
Co1···Co1 i2.8068 (14)O3—Co1—O5100.55 (13)
O3—Co1—O2 i89.66 (13)
O1—Co1—O390.06 (13)O5—Co1—O4 i95.88 (13)
O1—Co1—O4 i86.15 (14)
(a) Symmetry code: i = −x + 1/2, −y + 3/2, −z + 3/2.
Table 3. Selected bond lengths (Å) and angles (°) for [Co2(pdi)(DMF)3]·2(DMF)·H2O (a).
Table 3. Selected bond lengths (Å) and angles (°) for [Co2(pdi)(DMF)3]·2(DMF)·H2O (a).
InteractionBond Length [Å]InteractionAngles [°]
Co1—O12.072 (3)O10—Co1—O5 i91.01 (16)
Co1—O3 ii2.040 (3)O10—Co1—O1191.32 (16)
Co1—O5 i2.105 (3)O10—Co1—O189.36 (16)
Co1—O92.128 (4)O10—Co1—O991.85 (17)
Co1—O102.069 (4)O11—Co1—O5 i93.69 (14)
Co1—O112.097 (3)O11—Co1—O986.46 (15)
Co2—O21.993 (3)
Co2—O4 ii2.037 (3)O2—Co2—O5 i106.59 (15)
Co2—O5 i2.105 (3)O2—Co2—O4 ii94.93 (15)
Co2—O6 i2.270 (4)O2—Co2—O7 iii153.89 (13)
Co2—O7 iii2.265 (4)O2—Co2—O8 iii93.13 (14)
Co2—O8 iii2.050 (3)O2—Co2—O6 i94.23 (15)
O4 ii—Co2—O5 i100.40 (13)
O1—Co1—O5 i97.97 (13)O4 ii—Co2—O7 iii95.87 (14)
O1—Co1—O11168.31 (14)O4 ii—Co2—O8 iii108.82 (15)
O1—Co1—O981.86 (14)O4 ii—Co2—O6 i160.17 (13)
O3 ii—Co1—O5 i86.19 (14)O5 i—Co2—O7 iii94.72 (13)
O3 ii—Co1—O1188.10 (15)O5 i—Co2—O6 i60.06 (12)
O3 ii—Co1—O191.80 (15)O8 iii—Co2—O5 i143.07 (13)
O3 ii—Co1—O990.95 (15)O8 iii—Co2—O7 iii60.87 (13)
O3 ii—Co1—O10177.10 (16)O8 iii—Co2—O6 i88.18 (14)
    
Co1—Co23.368 (1)Co2 iv—O5—Co1 iv106.27 (14)
(a) Symmetry code: i = −x + 1/2, −y + 3/2, −z + 3/2; ii = −x + 3/2, y, −z + 1; iii = −x, −y + 1, −z + 1; iv = x + 1/2, −y + 3/2, z.
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Vollrath, A.; Liu, X.; Jansen, N.; Seiffert, P.; Geller, D.; Janiak, C. Cobalt Coordination Networks Based on the Linker (Phenazine-5,10-diyl)di- and Tetrabenzoate. Crystals 2026, 16, 185. https://doi.org/10.3390/cryst16030185

AMA Style

Vollrath A, Liu X, Jansen N, Seiffert P, Geller D, Janiak C. Cobalt Coordination Networks Based on the Linker (Phenazine-5,10-diyl)di- and Tetrabenzoate. Crystals. 2026; 16(3):185. https://doi.org/10.3390/cryst16030185

Chicago/Turabian Style

Vollrath, Annette, Xiang Liu, Nikolas Jansen, Philipp Seiffert, David Geller, and Christoph Janiak. 2026. "Cobalt Coordination Networks Based on the Linker (Phenazine-5,10-diyl)di- and Tetrabenzoate" Crystals 16, no. 3: 185. https://doi.org/10.3390/cryst16030185

APA Style

Vollrath, A., Liu, X., Jansen, N., Seiffert, P., Geller, D., & Janiak, C. (2026). Cobalt Coordination Networks Based on the Linker (Phenazine-5,10-diyl)di- and Tetrabenzoate. Crystals, 16(3), 185. https://doi.org/10.3390/cryst16030185

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