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Communication

Heteroleptic Cobalt Complexes with Catecholate and 1,4-Diaza-1,3-butadiene Ligands

by
Irina V. Ershova
1,
Maxim V. Arsenyev
1,
Ilya A. Yakushev
2 and
Alexandr V. Piskunov
1,*
1
G. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, 49 Tropinina Str., 603950 Nizhny Novgorod, Russia
2
N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii Prosp. 31, 119991 Moscow, Russia
*
Author to whom correspondence should be addressed.
Molbank 2025, 2025(1), M1972; https://doi.org/10.3390/M1972
Submission received: 27 January 2025 / Revised: 14 February 2025 / Accepted: 20 February 2025 / Published: 23 February 2025
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Abstract

:
Two new heteroleptic cobalt(II) complexes (3,6-Cat)Co(R-DAD) (where (3,6-Cat)2− is a dianion of 3,6-di-tert-butyl-o-benzoquinone, R-DAD is diisopropyl-1,4-diaza-1,3-butadiene (R = i-Pr (1)) or dicyclohexyl-1,4-diaza-1,3-butadiene (R = c-Hex (2)) have been synthesized and characterized in detail by IR, UV–Vis–NIR spectroscopy, and elemental analysis. The molecular structure of 1 was determined by X-ray diffraction analysis. Magnetic properties of 1 and 2 were measured both in a solid state and in a solution. According to the single-crystal X-ray diffraction analysis, the metal ion in 1 has a planar coordination environment, but magnetic susceptibility measurements of the microcrystalline samples of 1 and 2 indicate the formation of both forms with tetrahedral (d7, h.s., SCo = 3/2) and planar (d7, l.s., SCo = ½) coordination environments of the metal ion. Absorption spectra of crystalline samples of 1 and 2 possess intense absorption band in the NIR region. Electrochemical measurements of 1 and 2 were also performed.

Graphical Abstract

1. Introduction

Ligand-to-ligand charge transfer (LL’CT) chromophores contain donor (D) and acceptor (A) organic moieties coordinated to the metal center (M). The schematic representation of the simplest LL’CT chromophore is D-M-A. In LL’CT chromophores of the D-M-A type, charge separation occurs at the molecular level and allows the observation of a photoinduced intramolecular charge transfer process, consisting of the transition from the HOMO of the electron-saturated donor ligand to the LUMO of the electron-deficient acceptor ligand. A low-energy LL’CT is generally realized when the planarity of a coordination environment of the metal center is provided. Therefore, Ni [1,2,3,4,5,6], Pd [1,4,7,8,9,10,11], and Pt [4,7,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25] derivatives that prefer a square planar coordination polyhedron have received the most attention as D-M-A systems. The “α-diimine-MII-catecholate” complexes contain two differently charged redox-active ligands: the neutral α-diimine acts as an acceptor and a catecholate dianion as a donor. A steric effect of the ligands becomes a decisive factor in the possibility of obtaining the square planar “α-diimine-MII-catecholate” species for the derivatives of transition metals other than the group 10 metals, since the bulky ligands contribute to distortion of the planarity of the complexes. There are only a few examples of the 3d-row metal (Co [26,27,28] and Cu [29,30,31,32,33]) CT complexes, as four-coordinated copper or cobalt complexes are known to be coordinatively unsaturated compounds [34]. Thus, variations in ligand bulk can lead to either oligomerization [27,32,35,36,37,38] or deviation of the coordination polyhedron from planarity [34,39,40,41] with a corresponding change in the nature of charge transfer. Recently, “α-diimine-CoII-catecholate” complexes have been found to exhibit impressive antibacterial and anticancer activities [38], so this type of compound is of great research interest. The present work is devoted to the synthesis of square planar heteroleptic cobalt(II) D-M-A complexes based on catecholate and 1,4-diaza-1,3-butadiene ligands.

2. Results

To avoid the distortion of the square planar geometry in solutions of heteroleptic cobalt derivatives (3,6-Cat)Co(R-DAD), observed previously for the complex with 2,6-di(isopropyl)phenyl) substituted DAD ligand [28], complexes with less sterically hindered R substituents in the diimine ligand (R = i-Pr (1), c-Hex (2)) were synthesized by the reaction of anhydrous CoCl2 with equimolar quantities of R-DAD and ((3,6-Cat)Na2 (Scheme 1).
Complexes 1 and 2 were isolated from the reaction mixtures as the dark blue crystalline substances. Complexes 1 and 2 are extremely sensitive to atmospheric oxygen and moisture in solution, but are quite stable as crystalline samples exposed to air for at least several hours. They are highly soluble in THF, have moderate solubility in dichloromethane, poorly soluble in toluene, and are insoluble in saturated hydrocarbons. The composition and structure of 1 and 2 were determined by spectroscopic methods (IR, UV–Vis–NIR spectroscopy) and by elemental analysis. The 1H NMR spectra of the paramagnetic complexes 1 and 2 are not informative, because they are unresolved due to extreme broadening and signals shifting.
The molecular structure of 1 was determined by single-crystal X-ray diffraction (SC XRD); unfortunately, we have failed to obtain crystals of 2, suitable for X-ray study. According to the SC XRD data, 1 crystallizes in the trigonal R-3 space group with a unique complex molecule in an asymmetric unit. The Co2+ cation in 1 has an almost perfect square planar coordination environment formed by the oxygen atoms of the catecholate and the nitrogen atoms of the α-diimine ligands (Figure 1). The angle between mean planes of the metallacycles CoOCCO and CoNCCN is only 5.31°. The geometric parameters τ4 and τ4′ [42,43], which are used as a simple metrics for quantitative evaluation of the geometry of four-coordinate complexes (they range from 1.00 for a perfect tetrahedral geometry to 0 for a perfect square planar geometry), are 0.056 and 0.054, respectively.
The C(1)–O(1) (1.3664(16) Å) and C(2)–O(2) (1.3614(18) Å) bond lengths are in the range characteristic of C–O single bonds of catecholate metal complexes [44,45]. The C–C bond lengths in the C(1)–C(6) aromatic ring of the catecholate ligand (1.384(2)–1.408(2) Å, average value 1.398 Å) are similar to those in benzene (1.40 Å). The Co(1)–O(1) (1.8094(11) Å) and Co(1)–O(2) (1.8166(10) Å) bond lengths and Co(1)–N(1) (1.8778 (12) Å) and Co(1)–N(2) (1.8679(14) Å) are close to Co–O and Co–N distances in (3,6-Cat)Co(R-DAD) complexes [26,28]. Thus, according to the bond length distribution, the electronic structure of 1 in a single crystal is a catecholate of cobalt(II) with a neutrally coordinated 1,4-diaza-1,3-butadiene.
The electronic absorption spectra of complexes 1 and 2 were recorded in the range of 200–1100 nm in three organic solvents (toluene, DCM, THF) at 298 K (Figure 2). In all recorded spectra, there is a high-intensity absorption band in the near-UV region corresponding to the π-π* transitions in aromatic compounds. The visible and near-IR regions of spectra 1 and 2, recorded in DCM and THF, contain a broad low-intensity absorption band (716 nm, ε = 300 M−1 cm−1 (in DCM) and 732 nm, ε = 902 M−1 cm−1 (in THF) for 1; 699 nm, ε = 970 M−1 cm−1 (in DCM) and 716 nm, ε = 1799 M−1 cm−1 (in THF) for 2), corresponding to the LL’CT between Cat and DAD ligands, but this band is barely distinguishable in the toluene solutions (715 nm, ε = 111 M−1 cm−1; 719 nm, ε = 391 M−1 cm−1 for 1 and 2, respectively). The low-intensity and the negligible solvatochromic shift of the discussed absorption band indicate the structural distortion from planarity to tetrahedron as it was observed for (3,6-Cat)Co(dipp-DAD) [28].
Indeed, the values of the magnetic moment (µeff are 4.09 μB and 4.10 μB for 1 and 2, respectively) measured at 298 K in the DCM solution of the complexes by the Evans method (see the Supplementary Materials) are in a good agreement with the spin-only value of 3.87 μB for one paramagnetic center with spin S = 3/2, corresponding to the tetrahedral coordination environment of the high-spin Co2+ ion (d7, h.s., SCo = 3/2). The increased values of the µeff for high-spin Co(II) complexes have been attributed to the enhanced spin–orbit interactions [46] and are typical for other high-spin Co(II) complexes with redox-active ligands [28,47].
In the spectra recorded for solid samples of complexes 1 and 2 in Nujol, the band corresponding to the LL’CT is red-shifted at about 100 nm and has a significantly higher intensity (Figure 3).
The magnetic susceptibility of crystalline samples 1 and 2 was measured in the temperature range 5–300 K (Figure S3, see the Supplementary Materials). The high-temperature μeff values for the complexes (3.14 μB in 1, 3.26 μB in 2) are significantly higher than the spin-only value of 1.73 μB for the CoII ion in the low-spin state (d7, l.s., SCo = ½), which is characteristic for a square planar coordination environment of the CoII ion, and are lower than the spin-only value of 3.87 μB for the CoII ion in a high-spin state (d7, h.s., SCo = 3/2), which is characteristic for a tetrahedral coordination environment of the CoII ion. So, as in the case of (3,6-Cat)Co(dipp-DAD), the magnetic susceptibility measurements of the polycrystalline samples of 1 and 2 indicate the presence of two forms of (3,6-Cat)Co(DAD) in the mixture-square planar (d7, l.s., SCo = ½) and tetrahedral (d7, h.s., SCo = 3/2). Thus, the reduction in steric hindrance in diimine ligands does not prevent the distortion of the planarity in (3,6-Cat)Co(DAD) complexes.
Electrochemical measurements were carried out for complexes 1 and 2 in DCM solution (Figure 4). The redox processes in the ligands (oxidation of catecholate and reduction of diazabutadiene) proceed with the participation of the metal center, as we have previously shown for the complex [(3,6-Cat)Co(bipytBu)]2 [27]. In addition, an irreversible reduction peak corresponding to the CoII → CoI reduction is observed in the CVs of 1 and 2.

3. Materials and Methods

3.1. General Information

All operations for the synthesis of (3,6-Cat)Co(R-DAD) (R = i-Pr (1), c-Hex (2)) were carried out in the absence of atmospheric oxygen and moisture. Solvents were purified using standard methods [48]. Commercial reagents (sodium, anhydrous CoCl2) were purchased from Aldrich. 3,6-di-tert-butyl-o-benzoquinone [49], diisopropyl-1,4-diaza-1,3-butadiene, and dicyclohexyl-1,4-diaza-1,3-butadiene [50] were synthesized according to the literature procedures. The disodium salt of 3,6-di-tert-butyl-o-benzoquinone (3,6-Cat)Na2 was synthesized by the reduction of 3,6-di-tert-butyl-o-benzoquinone with sodium [51] and used in situ.
Elemental analyses were performed using the elemental analyzer Elementar Vario EL cube. An FSM 1201 spectrometer was employed to record IR spectra in Nujol. The electronic spectra of the complexes were recorded on a Perkin–Elmer Lambda 25 UV/Vis spectrometer (range: 220–1100 nm) at ambient temperature. 1H NMR spectra of 1 and 2 acquired using the static Evans’ method were recorded on a Bruker Avance III (400 MHz) spectrometer using tetramethylsilane as an internal standard. The magnetic susceptibility of the polycrystalline complexes was measured with a Quantum Design MPMS XL SQUID magnetometer in the temperature range 2–300 K with a magnetic field of up to 5 kOe. None of the complexes exhibited any field dependence of molar magnetization at low temperatures. Diamagnetic corrections were made using the Pascal constants. The effective magnetic moment was calculated as μeff(T) = [(3k/NAμB2)χT]1/2 ≈ (8χT)1/2.
Electrochemical studies were carried out using a Smartstat PS-50 potentiostat in a three-electrode mode. A glassy carbon (d = 2 mm) disk was used as the working electrode, a platinum wire was used as the auxiliary electrode, and Ag/AgCl/KCl (sat.) with a watertight diaphragm was used as the reference electrode. All measurements were carried out under argon. The samples were dissolved in pre-deaerated dichloromethane. The scan rate was 0.2 V s−1. The supporting electrolyte 0.1 M [(n-Bu)4N]ClO4 (99%, “Acros”) was twice recrystallized from aqueous ethanol and dried in a vacuum (48 h) at 50 °C. The concentration of the complexes was 2 × 10−3 M. The redox potentials are recalculated to the FcH/FcH+ (E1/2 = 0.50 V vs. Ag/AgCl/KCl (sat.)).

3.2. Synthesis of 1 and 2

A colorless solution of 1,4-diaza-1,3-butadiene (0.68 mmol) in dry THF (5 mL) was mixed with a blue suspension of an anhydrous CoCl2 (88.5 mg, 0.68 mmol) in the same solvent (10 mL) to give a deep green solution. Interaction of the resulting mixture with a pale yellow solution of (3,6-Cat)Na2 (0.68 mmol) in THF (10 mL) results in an immediate change in the reaction color to deep blue. The solvent was evaporated under reduced pressure, the dry residue was dissolved in toluene (30 mL), and the reaction mixture was separated from the NaCl precipitate by filtration. After concentration of the filtrate, the fine-crystalline product was precipitated. The dark blue precipitate of (3,6-Cat)Co(R-DAD) was collected by filtration and dried under vacuum. The single crystal used for the XRD analysis of 1 was obtained by slow cooling of the mother liquor (in toluene).
(1,4-di-iso-propyl-1,4-diazabutadiene-1,3)(3,6-di-tert-butyl-catecolato)cobalt(II) (3,6-Cat)Co(i-Pr-DAD) (1) Yield 163 mg (57%). Elemental analysis: Calculated (%) for C22H36CoN2O2: C 62.99, H 8.65, N 6.68; Found (%): C 63.29, H 8.86, N 6.55. UV–vis nm (ε, M−1 cm−1): 233 (12,313), 300 (5971), 716 (300) (in DCM); 226 (24,325), 301 (12,366), 732 (902) (in THF); 285 (15,909), 719 (111) (in toluene). IR (Nujol, KBr) cm−1: 1656 (w), 1631 (w), 1548 (m), 1444 (s), 1364 (s), 1355 (s), 1343 (s), 1287 (m), 1276 (m), 1237 (w), 1204 (m), 1169 (m), 1137 (m), 1067 (w), 1027 (w), 982 (m), 967 (m), 953 (s), 934 (w), 903 (w), 824 (m), 807 (w), 795 (w), 700 (w), 671 (w), 654 (m), 612 (w), 507 (w), 484 (w).
(1,4-di-cyclo-hexyl-1,4-diazabutadiene-1,3)(3,6-di-tert-butyl-catecolato)cobalt(II) (3,6-Cat)Co(c-Hex-DAD) (2) Yield 167 mg (49%). Elemental analysis: Calculated (%) for C28H44CoN2O2: C 67.31, H 8.88, N 5.61; Found (%): C 67.56, H 9.02, N 5.48. UV–vis nm (ε, M−1 cm−1): 233 (14,585), 294 (6603), 699 (970) (in DCM); 231 (25,933), 296sh (11,634), 716 (1799) (in THF); 285 (12,615), 719 (391) (in toluene). IR (Nujol, KBr) cm−1: 1623 (w), 1546 (w), 1405 (s), 1395 (s), 1353 (s), 1285 (m), 1270 (s), 1237 (s), 1202 (m), 1154 (w), 1140 (w), 1110 (w), 1096 (w), 1081 (w), 1027 (w), 982 (s), 963 (m), 953 (m), 942 (m), 926 (w), 893 (w), 836 (w), 822 (w), 810 (w), 793 (m), 693 (w), 654 (m), 616 (m), 523 (w), 504 (w), 465 (w).

3.3. Single-Crystal X-Ray Structure Analysis

The experimental X-ray data for compound 1 was obtained using a Bruker D8 Venture instrument (Mo Kα radiation, λ = 0.71073 Å) in φ- and ω-scan mode at the Center for Collective Use of the Kurnakov Institute RAS (Moscow, Russia) at 150 K. The collected raw data for 1 was treated with the APEX3 program suite [52], and experimental intensities for 1 were corrected for absorption effects using SADABS [53]. The structure was solved by direct methods and refined by full-matrix least-squares on F2 with anisotropic thermal parameters for all non-hydrogen atoms [54,55]. Residual electronic density, belonging to heavily disordered guest solvent molecules in the crystal structure was removed from the final refinement model using the PLATON SQUEEZE algorithm [56]. The hydrogen atoms were placed in calculated positions and refined using a riding model with dependent isotropic displacement parameters [Uiso(H) = 1.5Ueq(C) for methyl groups and Uiso(H) = 1.2Ueq(C) for all other H-atoms. All calculations were carried out using the SHELXTL [57] program suite and OLEX2 X-ray data visualization program package [58].
Crystal data for 1: C22H36CoN2O2, M = 419.46, R-3, a = 27.1126(8) Å, b = 27.1126(8) Å, c = 17.6679(5) Å, V = 11,247.5(7) Å3, Z = 18, dcalc = 1.115 g/cm3. A dark prism single crystal with dimensions 0.24 × 0.18 × 0.17 mm was selected and intensities of 105,967 reflections were collected (μ = 0.702 mm−1, θmax = 30.52°). After merging equivalence reflections and absorption corrections, 7633 independent reflections (Rint = 0.0583) were used for the structure solution and refinement. Final R factors R1 = 0.0373 [for 5833 reflections with F2 > 2σ(F2)], wR2 = 0.1013 (for all reflections), S = 1.033, and largest diff. peak and hole are 0.58 and −0.42 e/Å3, respectively.
CCDC 2418999 contains the supplementary crystallographic data. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif (accessed on 21 February 2025).

4. Conclusions

Two new cobalt(II) complexes with catecholate and 1,4-diaza-1,3-butadiene ligands have been synthesized. The aim of the current research was to obtain planar cobalt complexes, since this coordination geometry provides the best CT from donor (catecholate) to acceptor (DAD). Although the cobalt ion has a square planar coordination environment according to SC XRD data, the microcrystalline samples of the complexes contain a mixture of tetrahedral and planar species, and solutions of the complexes contain predominantly molecules with tetrahedral geometry. Thus, it was found that the use of less sterically hindered DAD ligands does not prevent the distortion of the square planar geometry in solutions of heteroleptic cobalt derivatives (3,6-Cat)Co(R-DAD).

Supplementary Materials

Figure S1: 1H NMR spectrum of 1 acquired using the static Evans’ method; Figure S2: 1H NMR spectrum of 2 acquired using the static Evans’ method; Equation to determine magnetic susceptibility by Evans method; Figure S3: Temperature dependences of the effective magnetic moment (μeff) of complexes (3,6-Cat)Co(R-DAD) (R = i-Pr (1), c-Hex (2)); Figure S4: IR spectrum of 1; Figure S5: IR spectrum of 2. References [59,60,61,62] are cited in the supplementary materials.

Author Contributions

Investigation, writing—original draft preparation, I.V.E.; formal analysis, investigation, M.V.A.; formal analysis, I.A.Y.; supervision, writing—review and editing, A.V.P. All authors have read and agreed to the published version of the manuscript.

Funding

This research was carried out as part of a state assignment of IOMC RAS.

Data Availability Statement

CCDC 2418999 contains the supplementary crystallographic data for this paper. These data are provided free of charge by the Cambridge Crystallographic Data Centre: https://www.ccdc.cam.ac.uk/structures (accessed on 21 February 2025).

Acknowledgments

This research was conducted utilizing the analytical facilities of the G.A. Razuvaev Institute of Organometallic Chemistry’s Analytical Center, Russian Academy of Sciences. The experimental studies of the single crystal structure were performed at the Center for Collective Use of the Kurnakov Institute RAS (Moscow, Russia). The authors thank A.S. Bogomyakov (ITC SB RAS, Novosibirsk) for the magnetic susceptibility measurements for solid samples.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Brasse, M.; Cámpora, J.; Davies, M.; Teuma, E.; Palma, P.; Álvarez, E.; Sanz, E.; Reyes, M.L. Integrating Catalyst and Co-Catalyst Design in Olefin Polymerization Catalysis: Transferable Dianionic Ligands for the Activation of Late Transition Metal Polymerization Catalysts. Adv. Synth. Catal. 2007, 349, 2111–2120. [Google Scholar] [CrossRef]
  2. Kramer, W.W.; Cameron, L.A.; Zarkesh, R.A.; Ziller, J.W.; Heyduk, A.F. Donor–Acceptor Ligand-to-Ligand Charge-Transfer Coordination Complexes of Nickel(II). Inorg. Chem. 2014, 53, 8825–8837. [Google Scholar] [CrossRef]
  3. Cameron, L.A.; Ziller, J.W.; Heyduk, A.F. Near-IR absorbing donor–acceptor ligand-to-ligand charge-transfer complexes of nickel(II). Chem. Sci. 2016, 7, 1807–1814. [Google Scholar] [CrossRef] [PubMed]
  4. Yamada, S.; Matsumoto, T.; Chang, H.-C. Impact of Group 10 Metals on the Solvent-Induced Disproportionation of o-Semiquinonato Complexes. Chem. Eur. J. 2019, 25, 8268–8278. [Google Scholar] [CrossRef] [PubMed]
  5. Pashanova, K.I.; Lazarev, N.M.; Zolotukhin, A.A.; Kovylina, T.A.; Petrov, B.I.; Piskunov, A.V. Thermal Behavior of the “α-Diimine-NiII-Catecholate” Chromophores. Chem. Sel. 2024, 9, e202304536. [Google Scholar] [CrossRef]
  6. Pashanova, K.I.; Yakushev, I.A.; Lazarev, N.M.; Zolotukhin, A.A.; Kovylina, T.A.; Klimashevskaya, A.V.; Arsenyev, M.V.; Sulimova, O.V.; Dorovatovskii, P.V.; Piskunov, A.V. “Diimine–NiII–Catecholate” Chromophores Based on Phenanthroline-Type Ligand Systems: Molecular Structure, Ligand-to-Ligand Charge Transfer, and Thermal Behavior. Russ. J. Inorg. Chem. 2024, 69, 1671–1684. [Google Scholar] [CrossRef]
  7. Ghosh, P.; Begum, A.; Herebian, D.; Bothe, E.; Hildenbrand, K.; Weyhermüller, T.; Wieghardt, K. Coordinated o-Dithio- and o-Iminothiobenzosemiquinonate(1−) π Radicals in [MII(bpy)(L.)](PF6) Complexes. Angew. Chem. Int. Ed. 2003, 42, 563–567. [Google Scholar] [CrossRef] [PubMed]
  8. Roy, R.; Chattopadhyay, P.; Sinha, C.; Chattopadhyay, S. Synthesis, spectral and electrochemical studies of arylazopyridine complexes of palladium(ii) with dioxolenes. Polyhedron 2006, 15, 3361–3369. [Google Scholar] [CrossRef]
  9. Deibel, N.; Schweinfurth, D.; Fiedler, J.; Záliš, S.; Sarkar, B. Isomeric separation in donor–acceptor systems of Pd(ii) and Pt(ii) and a combined structural, electrochemical and spectroelectrochemical study. Dalton Trans. 2011, 40, 9925–9934. [Google Scholar] [CrossRef] [PubMed]
  10. BaniKhaled, M.O.; Becker, J.D.; Koppang, M.; Sun, H. Perfluoroalkylation of Square-Planar Transition Metal Complexes: A Strategy To Assemble Them into Solid State Materials with a π–π Stacked Lamellar Structure. Cryst. Growth Des. 2016, 16, 1869–1878. [Google Scholar] [CrossRef]
  11. Tahara, K.; Ashihara, Y.; Higashino, T.; Ozawa, Y.; Kadoya, T.; Sugimoto, K.; Ueda, A.; Morib, H.; Abe, M. New π-extended catecholato complexes of Pt(ii) and Pd(ii) containing a benzothienobenzothiophene (BTBT) moiety: Synthesis, electrochemical behavior and charge transfer properties. Dalton Trans. 2019, 48, 7367–7377. [Google Scholar] [CrossRef]
  12. Rauth, G.K.; Pal, S.; Das, D.; Sinha, C.; Slawin, A.M.Z.; Woollins, J.D. Synthesis, spectral characterization and electrochemical studies of mixed-ligand complexes of platinum(II) with 2-(arylazo)pyridines and catechols. Single-crystal X-ray structure of dichloro{2-(phenylazo) pyridine}platinum(II). Polyhedron 2001, 20, 363–372. [Google Scholar] [CrossRef]
  13. Sarkar, B.; Hübner, R.; Pattacini, R.; Hartenbach, I. Combining two non-innocent ligands in isomeric complexes [Pt(pap)mQn]0 (pap = phenylazopyridine, Q = 3,5-di-tert-butyl-benzoquinone. Dalton Trans. 2009, 38, 4653–4655. [Google Scholar] [CrossRef]
  14. Best, J.; Sazanovich, I.V.; Adams, H.; Bennett, R.D.; Davies, E.S.; Meijer, A.J.H.M.; Towrie, M.; Tikhomirov, S.A.; Bouganov, O.V.; Ward, M.D.; et al. Structure and Ultrafast Dynamics of the Charge-Transfer Excited State and Redox Activity of the Ground State of Mono- and Binuclear Platinum(II) Diimine Catecholate and Bis-catecholate Complexes: A Transient Absorption, TRIR, DFT, and Electrochemical Study. Inorg. Chem. 2010, 49, 10041–10056. [Google Scholar] [CrossRef] [PubMed]
  15. Liua, W.; Heinze, K. Rhenium(i) and platinum(ii) complexes with diimine ligands bearing acidic phenol substituents: Hydrogen-bonding, acid–base chemistry and optical properties. Dalton Trans. 2010, 39, 9554–9564. [Google Scholar] [CrossRef]
  16. Deibel, N.; Schweinfurth, D.; Hohloch, S.; Fiedler, J.; Sarkar, B. Donor–acceptor systems of Pt(ii) and redox-induced reactivity towards small molecules. Chem. Commun. 2012, 48, 2388–2390. [Google Scholar] [CrossRef] [PubMed]
  17. Yang, J.; Kersi, D.K.; Giles, L.J.; Stein, B.W.; Feng, C.; Tichnell, C.R.; Shultz, D.A.; Kirk, M.L. Ligand Control of Donor–Acceptor Excited-State Lifetimes. Inorg. Chem. 2014, 53, 4791–4793. [Google Scholar] [CrossRef] [PubMed]
  18. Scattergood, P.A.; Jesus, P.; Adams, H.; Delor, M.; Sazanovich, I.V.; Burrows, H.D.; Serpa, C.; Weinstein, J.A. Exploring excited states of Pt(II) diimine catecholates for photoinduced charge separation. Dalton Trans. 2015, 44, 11705–11716. [Google Scholar] [CrossRef]
  19. Yang, J.; Kersi, D.K.; Richers, C.P.; Giles, L.J.; Dangi, R.; Stein, B.W.; Feng, C.; Tichnell, C.R.; Shultz, D.A.; Kirk, M.L. Ground State Nuclear Magnetic Resonance Chemical Shifts Predict Charge-Separated Excited State Lifetimes. Inorg. Chem. 2018, 57, 13470–13476. [Google Scholar] [CrossRef] [PubMed]
  20. Kirk, M.L.; Shultz, D.A.; Hewitt, P.; Stasiw, D.E.; Chen, J.; Est, A.v.d. Chromophore-radical excited state antiferromagnetic exchange controls the sign of photoinduced ground state spin polarization. Chem. Sci. 2021, 12, 13704–13710. [Google Scholar] [CrossRef]
  21. Kirk, M.L.; Shultz, D.A.; Hewitt, P.; Chen, J.; Est, A.v.d. Excited State Magneto-Structural Correlations Related to Photoinduced Electron Spin Polarization. J. Am. Chem. Soc. 2022, 144, 12781–12788. [Google Scholar] [CrossRef] [PubMed]
  22. Kirk, M.L.; Shultz, D.A.; Marri, A.R.; Hewitt, P.; Est, A.v.d. Single-Photon-Induced Electron Spin Polarization of Two Exchange-Coupled Stable Radicals. J. Am. Chem. Soc. 2022, 144, 21005–21009. [Google Scholar] [CrossRef] [PubMed]
  23. Kirk, M.L.; Shultz, D.A.; Hewitt, P.; Marri, A.R.; van der Est, A. Competitive reversed quartet mechanisms for photogenerated ground state electron spin polarization. Chem. Sci. 2023, 14, 9689–9695. [Google Scholar] [CrossRef] [PubMed]
  24. Shultz, D.A.; Stephenson, R.; Kirk, M.L. Dinuclear ligand-to-ligand charge transfer complexes. Dalton Trans. 2023, 52, 1970–1976. [Google Scholar] [CrossRef] [PubMed]
  25. Kirk, M.L.; Shultz, D.A.; Marri, A.R.; van der Est, A. Photoinduced Magnetic Exchange-Jump Promotes Ground State Biradical Electron Spin Polarization. J. Am. Chem. Soc. 2024, 146, 9285–9292. [Google Scholar] [CrossRef]
  26. Bubnov, M.P.; Teplova, I.A.; Druzhkov, N.O.; Fukin, G.K.; Cherkasova, A.V.; Cherkasov, V.K. Catecholato complexes of cobalt and nickel with 1,4-disubstituted-1,4-diazabutadiens-1,3 and 1,2-bis(diphenylphosphino)ethane. J. Chem. Sci. 2015, 127, 527–535. [Google Scholar] [CrossRef]
  27. Pashanova, K.I.; Ershova, I.V.; Trofimova, O.Y.; Rumyantsev, R.V.; Fukin, G.K.; Bogomyakov, A.S.; Arsenyev, M.V.; Piskunov, A.V. Charge Transfer Chromophores Derived from 3d-Row Transition Metal Complexes. Molecules 2022, 27, 8175. [Google Scholar] [CrossRef] [PubMed]
  28. Pashanova, K.I.; Ershova, I.V.; Yakushev, I.A.; Meshcheryakova, I.N.; Arsenyev, M.V.; Piskunov, A.V. Intramolecular charge transfer in bulky “diazabutadiene-M(II)-catecholate” chromophores (M = Ni, Co): A role of a molecular geometry. Polyhedron 2023, 243, 116527. [Google Scholar] [CrossRef]
  29. Brown, D.G.; Reinprecht, J.T.; Vogel, G.C. Synthesis and characterization of copper(II) catecholato complexes. Inorg. Nucl. Chem. Lett. 1976, 12, 399–404. [Google Scholar] [CrossRef]
  30. Brown, D.G.; Hughes, W.J. Copper(II) Complexes Containing 3-n-Nonylcatechol: Preparation and Ligand Oxidation. Z. Naturforsch. B 1979, 34b, 1408–1412. [Google Scholar] [CrossRef]
  31. Brown, D.G.; Hughes, W.J.; Knerr, G. Electronic and X-ray photoelectron spectra of copper catecholate complexes. Inorg. Chim. Acta 1980, 46, 123–126. [Google Scholar] [CrossRef]
  32. Buchanan, R.M.; Wilson-Blumenberg, C.; Trapp, C.; Larsen, S.K.; Greene, D.L.; Pierpont, C.G. Counter ligand dependence of charge distribution in copper-quinone complexes. Structural and magnetic properties of (3,5-di-tert-butylcatecholato)(bipyridine)copper(II). Inorg. Chem. 1986, 25, 3070–3076. [Google Scholar] [CrossRef]
  33. Trofimova, O.Y.; Pashanova, K.I.; Ershova, I.V.; Arseniev, M.V.; Yakushev, I.A.; Dorovatovsky, P.V.; Aisin, R.R.; Piskunov, A.V. Copper(II) Catecholate Complexes with Polypyridyl Ligands. Russ. J. Inorg. Chem. 2023, 68, 1133–1142. [Google Scholar] [CrossRef]
  34. Pashanova, K.I.; Poddel’sky, A.I.; Piskunov, A.V. Complexes of “late” transition metals of the 3d row based on functionalized o-iminobenzoquinone type ligands: Interrelation of molecular and electronic structure, magnetic behaviour. Coord. Chem. Rev. 2022, 459, 214399. [Google Scholar] [CrossRef]
  35. Buchanan, R.M.; Fitzgerald, B.J.; Pierpont, C.G. Semiquinone radical anion coordination to divalent cobalt and nickel. Structural features of the bis(3,5-di-tert-butyl-1,2-semiquinone)cobalt(II) tetramer. Inorg. Chem. 1979, 18, 3439–3444. [Google Scholar] [CrossRef]
  36. Lynch, M.W.; Buchanan, R.M.; Pierpont, C.G.; Hendrickson, D.N. Weak magnetic exchange interactions between paramagnetic metal ions and coordinated o-semiquinones in M(9,10-phenanthrenesemiquinone)2(pyridine)2 [M = nickel(II) and cobalt(II)] and tetranuclear M4(o-emiquinone)8 complexes. Inorg. Chem. 1981, 20, 1038–1046. [Google Scholar] [CrossRef]
  37. Thompson, J.S.; Calabrese, J.C. Copper-catechol chemistry. Synthesis, spectroscopy, and structure of bis(3,5-di-tert-butyl-o-semiquinato)copper(II). J. Am. Chem. Soc. 1986, 108, 1903–1907. [Google Scholar] [CrossRef]
  38. Dutta, J.; Varshini, A.; Padaga, S.G.; Bera, A.; Sarkar, T.; Biswas, S.; Hussain, A. Red and NIR light-triggered enhancement of anticancer and antibacterial activities of dinuclear Co(ii)-catecholate complexes. Dalton Trans. 2025, 54, 3027–3038. [Google Scholar] [CrossRef] [PubMed]
  39. Poddel’sky, A.I.; Cherkasov, V.K.; Abakumov, G.A. Transition metal complexes with bulky 4,6-di-tert-butyl-N-aryl(alkyl)-o-iminobenzoquinonato ligands: Structure, EPR and magnetism. Coord. Chem. Rev. 2009, 253, 291–324. [Google Scholar] [CrossRef]
  40. Ershova, I.V.; Smolyaninov, I.V.; Bogomyakov, A.S.; Fedin, M.V.; Starikov, A.G.; Cherkasov, A.V.; Fukin, G.K.; Piskunov, A.V. Tetrahedral nickel(II) and cobalt(II) bis-o-iminobenzosemiquinonates. Dalton Trans. 2019, 48, 10723–10732. [Google Scholar] [CrossRef] [PubMed]
  41. Piskunov, A.V.; Pashanova, K.I.; Ershova, I.V.; Bogomyakov, A.S.; Starikov, A.G.; Cherkasov, A.V. Synthesis of four-, five-, and six-coordinate cobalt(III) bis-o-iminobenzosemiquinone complexes. Russ. Chem. Bull. 2019, 68, 757–769. [Google Scholar] [CrossRef]
  42. Yang, L.; Powell, D.R.; Houser, R.P. Structural variation in copper(I) complexes with pyridylmethylamide ligands: Structural analysis with a new four-coordinate geometry index, τ4. Dalton Trans. 2007, 36, 955–964. [Google Scholar] [CrossRef] [PubMed]
  43. Okuniewski, A.; Rosiak, D.; Chojnacki, J.; Becker, B. Coordination polymers and molecular structures among complexes of mercury(II) halides with selected 1-benzoylthioureas. Polyhedron 2015, 90, 47–57. [Google Scholar] [CrossRef]
  44. Maleeva, A.V.; Ershova, I.V.; Trofimova, O.Y.; Arsenyeva, K.V.; Yakushev, I.A.; Piskunov, A.V. Near-IR absorbing donor-acceptor charge-transfer gallium complex—An example from non-transition metal chemistry. Mendeleev Commun. 2022, 32, 83–86. [Google Scholar] [CrossRef]
  45. Klimashevskaya, A.V.; Arsenyeva, K.V.; Maleeva, A.V.; Druzhkov, N.O.; Arsenyev, M.V.; Cherkasov, A.V.; Yakushev, I.A.; Aysin, R.R.; Piskunov, A.V. Donor-Acceptor Tin(IV) Complexes with α-Diimine and Catecholate Ligands. Eur. J. Inorg. Chem. 2023, 26, e202300540. [Google Scholar] [CrossRef]
  46. König, E.; Kremer, S. Complete Theory of Paramagnetism in Transition Metal Ions III. The Octahedral and Tetrahedral d3 and d7 Electron Configurations. Ber. Bunsenges. Phys. Chem. 1974, 78, 786–795. [Google Scholar] [CrossRef]
  47. Ivakhnenko, E.P.; Starikov, A.G.; Minkin, V.I.; Lyssenko, K.A.; Antipin, M.Y.; Simakov, V.I.; Korobov, M.S.; Borodkin, G.S.; Knyazev, P.A. Synthesis, Molecular and Electronic Structures of Six-Coordinate Transition Metal (Mn, Fe, Co, Ni, Cu, and Zn) Complexes with Redox-Active 9-Hydroxyphenoxazin-1-one Ligands. Inorg. Chem. 2011, 50, 7022–7032. [Google Scholar] [CrossRef] [PubMed]
  48. Perrin, D.D.; Armarego, W.L.F.; Perrin, D.R. Purification of Laboratory Chemicals; Pergamon Press: Oxford, UK, 1980. [Google Scholar]
  49. Garnov, V.A.; Nevodchikov, V.I.; Abakumova, L.G.; Abakumov, G.A.; Cherkasov, V.K. New tetrahydro-2, 3-naphthoquinones. Bull. Acad. Sci. USSR Div. Chem. Sci. 1987, 36, 1728–1730. [Google Scholar] [CrossRef]
  50. Koten, G.V.; Vrieze, K. 1,4-Diaza-1,3-butadiene (α-Diimine) Ligands: Their Coordination Modes and the Reactivity of Their Metal Complexes. Adv. Organomet. Chem. 1982, 21, 151–239. [Google Scholar] [CrossRef]
  51. Lado, A.V.; Piskunov, A.V.; Cherkasov, V.K.; Fukin, G.K.; Abakumov, G.A. Free radical fixation by tin(IV) diphenylcatecholate complexes. Russ. J. Coord. Chem. 2006, 32, 173–179. [Google Scholar] [CrossRef]
  52. APEX3, SAINT and SADABS; Bruker AXS Inc.: Madison, WI, USA, 2016.
  53. Krause, L.; Herbst-Irmer, R.; Sheldrick, G.M.; Stalke, D. Comparison of silver and molybdenum microfocus X-ray sources for single-crystal structure determination. J. Appl. Crystallogr. 2015, 48, 3–10. [Google Scholar] [CrossRef] [PubMed]
  54. Sheldrick, G.M. A short history of SHELX. Acta Crystallogr. Sect. A Found. Crystallogr. 2008, 64, 112–122. [Google Scholar] [CrossRef]
  55. Sheldrick, G.M. SHELXT—Integrated space-group and crystal-structure determination. Acta Crystallogr. Sect. A Found. Crystallogr. 2015, 71, 3–8. [Google Scholar] [CrossRef] [PubMed]
  56. Spek, A.L. PLATON SQUEEZE: A tool for the calculation of the disordered solvent contribution to the calculated structure factors. Acta Crystallogr. Sect. C Struct. Chem. 2015, 71, 9–18. [Google Scholar] [CrossRef] [PubMed]
  57. Sheldrick, G.M. Crystal Structure Refinement with SHELXL. Acta Crystallogr. Sect. C Struct. Chem. 2015, 71, 3–8. [Google Scholar] [CrossRef] [PubMed]
  58. Dolomanov, O.V.; Bourhis, L.J.; Gildea, R.J.; Howard, J.A.K.; Puschmann, H. OLEX2: A complete structure solution, refinement and analysis program. J. Appl. Cryst. 2009, 42, 339–341. [Google Scholar] [CrossRef]
  59. Evans, D.F. The Determination of the Paramagnetic Susceptibility of Substances in Solution by Nuclear Magnetic Resonance. J. Chem. Soc. 1959, 2003–2005. [Google Scholar] [CrossRef]
  60. Live, D.H.; Chan, S.I. Bulk susceptibility corrections in nuclear magnetic resonance experiments using superconducting solenoids. Anal. Chem. 1970, 42, 791–792. [Google Scholar] [CrossRef]
  61. Schubert, E.M. Utilizing the Evans method with a superconducting NMR spectrometer in the undergraduate laboratory. J. Chem. Educ. 1992, 69, 62. [Google Scholar] [CrossRef]
  62. Carlin R., L. Magnetochemistry; Springer: Berlin/Heidelberg, Germany, 1986; 328p. [Google Scholar]
Molbank 2025 m1972 sch001
Scheme 1. Synthesis of complexes 1 and 2.
Scheme 1. Synthesis of complexes 1 and 2.
Molbank 2025 m1972 sch001
Molbank 2025 m1972 g001
Figure 1. Molecular structure of 1 (anisotropic displacement ellipsoids of heteroatoms drawn at the 50% probability level; H atoms are omitted for clarity).
Figure 1. Molecular structure of 1 (anisotropic displacement ellipsoids of heteroatoms drawn at the 50% probability level; H atoms are omitted for clarity).
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Figure 2. (a) Electronic absorption spectra of 1 recorded at 298 K (C = 10−4 mol L−1); (b) electronic absorption spectra of 2 recorded at 298 K (C = 10−4 mol L−1).
Figure 2. (a) Electronic absorption spectra of 1 recorded at 298 K (C = 10−4 mol L−1); (b) electronic absorption spectra of 2 recorded at 298 K (C = 10−4 mol L−1).
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Molbank 2025 m1972 g003
Figure 3. Electronic absorption spectra of complexes (3,6-Cat)Co(R-DAD) (R = i-Pr (1), c-Hex (2)) recorded at 298 K in Nujol mulls.
Figure 3. Electronic absorption spectra of complexes (3,6-Cat)Co(R-DAD) (R = i-Pr (1), c-Hex (2)) recorded at 298 K in Nujol mulls.
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Figure 4. Cyclic voltammograms of 1 and 2 in DCM solution, 0.1 M [(n-Bu)4N]ClO4, argon, 20 °C, GC working electrode. Potentials are referenced in volts vs. FcH/FcH+.
Figure 4. Cyclic voltammograms of 1 and 2 in DCM solution, 0.1 M [(n-Bu)4N]ClO4, argon, 20 °C, GC working electrode. Potentials are referenced in volts vs. FcH/FcH+.
Molbank 2025 m1972 g004
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Ershova, I.V.; Arsenyev, M.V.; Yakushev, I.A.; Piskunov, A.V. Heteroleptic Cobalt Complexes with Catecholate and 1,4-Diaza-1,3-butadiene Ligands. Molbank 2025, 2025, M1972. https://doi.org/10.3390/M1972

AMA Style

Ershova IV, Arsenyev MV, Yakushev IA, Piskunov AV. Heteroleptic Cobalt Complexes with Catecholate and 1,4-Diaza-1,3-butadiene Ligands. Molbank. 2025; 2025(1):M1972. https://doi.org/10.3390/M1972

Chicago/Turabian Style

Ershova, Irina V., Maxim V. Arsenyev, Ilya A. Yakushev, and Alexandr V. Piskunov. 2025. "Heteroleptic Cobalt Complexes with Catecholate and 1,4-Diaza-1,3-butadiene Ligands" Molbank 2025, no. 1: M1972. https://doi.org/10.3390/M1972

APA Style

Ershova, I. V., Arsenyev, M. V., Yakushev, I. A., & Piskunov, A. V. (2025). Heteroleptic Cobalt Complexes with Catecholate and 1,4-Diaza-1,3-butadiene Ligands. Molbank, 2025(1), M1972. https://doi.org/10.3390/M1972

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