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Article

Unprecedented Dinuclear CuII N,O-Donor Complex: Synthesis, Structural Characterization, Fluorescence Property, and Hirshfeld Analysis

by
Yin-Xia Sun
*,
Ying-Qi Pan
,
Xin Xu
and
Yang Zhang
School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou 730070, Gansu, China
*
Author to whom correspondence should be addressed.
Crystals 2019, 9(12), 607; https://doi.org/10.3390/cryst9120607
Submission received: 8 November 2019 / Revised: 16 November 2019 / Accepted: 18 November 2019 / Published: 20 November 2019
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Abstract

:
An unprecedented dinuclear CuII complex, [Cu2(L2)2], derived from a salamo-like chelating ligand H2L2, was produced by the cleavage of a newly synthesized, half-salamo-like ligand HL1 (2-[O-(1-ethyloxyamide)]oxime-3,5-dichloro-phenol). This was synthesized and characterized by elemental analyses, IR, UV–Vis and fluorescent spectra, single crystal X-ray diffraction analysis, and Hirshfeld surface analysis. X-ray crystallographic analysis indicated that the two CuII (Cu1 and Cu2) ions bore different (N2O3 and N2O2) coordination environments, the penta-coordinated Cu1 ion possessed a slightly twisted tetragonal pyramid geometry with the τ value τ = 0.004, and the tetra-coordinated Cu2 ion showed a slightly twisted square planar geometry. Interestingly, one oxime oxygen atom participated in the coordination reported previously. Moreover, an infinite two-dimensional layered supramolecular network was formed. Compared with HL1, the CuII complex possessed the characteristic of fluorescence quenching.

Graphical Abstract

1. Introduction

Salen-like ligand and its derivatives (R–CH=N–(CH2)n–N=CH–R) have received extensive attention in the field of coordination chemistry in the past decades. This is due to their use as essential Schiff bases. They can coordinate with alkaline earth, rare earth, and d-block transition metal ions to form stable mononuclear or multinuclear metal coordination compounds [1,2,3,4,5]. It has been found that these salen-like complexes have various special structures and interesting properties [6,7,8]. In recent years, based on the research of salen and its derivatives, a new salamo-like ligand and its derivatives (R–CH=N–O–(CH2)n–O–N=CH–R) have been developed, as the cavity formed by N2O2 is easier to bind with metal ions [9,10,11,12,13]. When different metal ions are added, mononuclear and multinuclear metal complexes with different structures are expected, which show superior stability and flexibility compared with salen-like compounds [14,15,16,17]. The salamo-like ligands and their metal complexes have special properties and potential applications. For example, they are widely used in the fields of magnetic materials [18,19,20,21], electrochemistry [22,23,24,25], catalysis [26,27,28,29,30], luminescence [31,32,33,34,35,36], ion recognition [37,38,39,40], biological antibacterial [41,42,43], and supramolecular architecture [44,45,46,47,48,49]. In addition, the potential applications of polynuclear metal N2O2-donor complexes in photoelectric, magnetic, and porous materials are interesting [50,51]. In the salamo-like metal complexes mentioned above, the metal ions always coordinate with the N2O2-donor cavities of salamo-like ligands, and at the same time, the metal ions can also coordinate with the three-position hydroxyl and alkoxy oxygen atoms from salicylaldehydes of salamo-like ligands, without the oxime oxygen atoms participating in the coordination reported previously. With the development of salamo-like metal complexes, the participation of oxime oxygen atoms of salamo-like ligands in coordination should be constantly emerging.
In order to study the structures and properties of metal salamo-like complexes, we have designed and synthesized a new half-salamo-like ligand, HL1, and a CuII complex [Cu2(L2)2]. The CuII complex [Cu2(L2)2] was obtained by the reaction of the ligand HL1 with Cu(OAc)2·H2O and contained no acetate ion. This contrasts with the salamo-like complexes previously reported [52,53], in which an acetate ion often accompanied and coordinated with metal ions. The fluorescence property and Hirshfeld surface analysis of the CuII complex were studied [54].

2. Experimental

2.1. Materials and Instrumentation

2-Hydroxy-3,5-dichlorobenzaldehyde of 99% purity was obtained from the Alfa Aesar. The other reagents and solvents used in the experiment were purchased from the Tianjin Chemical Reagent Factory at the analytical reagent level and used without further purification [55]. Elemental analyses of metal element (Cu) and non-metallic elements (C, H, and N) were measured by an atomic emission spectrometer (IRIS ER/S·WP-1 ICP) and automatic elemental detection analyzer (GmbH VariuoEL V3.00) from Berlin, Germany, respectively, melting points were measured by the use of a microscopic melting point apparatus made by the Beijing Taike Instrument Limited Company (Beijing, China) and was uncorrected, 1H NMR (nuclear magnetic resonance) spectra were measured by German Bruker AVANCE DRX-400/600 spectroscopy (Bruker AVANCE, Billerica, MA, USA), single crystal X-ray structure data was collected by a CCD surface detecting diffractometer (Bruker, Germany), and Mo-Kα (λ = 0.71073 Å) ray radiation was monochromated with graphite, IR spectra were recorded on a VERTEX 70 spectrophotometer with samples prepared as KBr (500–4000 cm−1) from Bruker, Germany, UV–Vis spectra were measured on a UV-3900 spectrophotometer from Hitachi, Tokyo, Japan, fluorescence spectra were recorded on a F-7000 FL 220-240V spectrophotometer from Hitachi, Tokyo, Japan, and Hirshfeld surface analysis of the CuII complex was performed using the Crystal Explorer program were all made according to similar methods previously reported [56].

2.2. Preparation of the Ligand HL1

The preparation of 1,2-bis(aminooxy)ethane has been reported in previous studies [57,58]. 2-Hydroxy-3,5-dichlorobenzaldehyde (382.02 mg, 2.0 mmol) in chloroform solution (30 mL) was slowly added to 1,2-bis(aminooxy)ethane (368.4 mg, 4.0 mmol) in chloroform solution (30 mL) for ~ 4–5 h. The mixture was heated and stirred at ~ 40–45 °C for 5 h. Finally, the mixed solution was concentrated under reduced pressure. The ligand HL1 (2-[O-(1-ethyloxyamide)]oxime-3,5-dichloro-phenol) was purified and obtained by column chromatography (v/v, chloroform/ethyl acetate = 20:1) (Scheme 1). Yield: 58.5%. m.p.: 58–60 °C. 1H NMR (500 MHz, CDCl3) δ 10.47 (s, 1H), 8.14 (s, 1H), 7.37 (s, 1H), 7.17 (s, 1H), 4.47 (d, J = 8.5 Hz, 2H), 3.98 (d, J = 5.0 Hz, 2H). IR (KBr, cm−1): 3438 (m), 2966 (m), 2953 (m), 2897 (m), 1737 (m), 1615 (s), 1470 (s), 1449 (m), 1385 (s), 1380 (s), 1347 (s), 1271 (s), 1214 (m), 1181 (s), 1067 (w), 978 (w), 940 (s), 850 (s), 742 (m), 662 (s), 601 (s), 532 (s). UV–Vis (CH3CH2OH), λmax: 266 and 324 nm. Anal. Calc. for C9H10Cl2N2O3 (%): C, 40.78; H, 3.80; N, 10.57. Found: C, 40.86; H, 3.96; N, 10.43.

2.3. Preparation of the CuII Complex

The synthetic route to the CuII complex is depicted in Scheme 2. An acetone solution (3 mL) of HL1 (10.60 mg, 0.04 mmol) was added to a methanol solution (3 mL) of Cu(OAc)2·H2O (7.96 mg, 0.04 mmol). The mixed solution was stirred for 15 min and then filtered into a vial, which was sealed with aluminum foil. About two weeks later, some bright brown block-like crystals suitable for X-ray diffraction were gained and collected carefully. Yield: 54.5%. IR (KBr, cm−1): 3423 (m), 2992 (m), 2945 (m), 2926 (m), 1609 (s), 1507 (s), 1443 (m), 1396 (s), 1358 (m), 1320 (s), 1263 (s), 1205 (s), 1169 (w), 1073 (s), 973 (w), 949 (s), 864 (m), 759 (s), 693 (s), 626 (s), 559 (w), 531 (w). UV–Vis (CH3CH2OH), λmax (nm): 271 and 382 nm. Anal. Calc. for C32H20Cl8Cu2N4O8 (%): C, 38.46; H, 2.02; N, 5.61; Cu, 12.72. Found: C, 38.61; H, 1.86; N, 5.48; Cu, 12.65.

2.4. Crystal Structure Determination of the CuII Complex

The crystal structure determination of the CuII complex is given in the Supplementary Materials. The key crystal data and structural parameters of the CuII complex are summarized in Table 1. CCDC: 1959387.

3. Results and Discussion

3.1. Infrared Spectra

The infrared spectra of HL1 and the CuII complex exhibited various bands in the 500–4000 cm−1 range. As shown in Table 2 and Figure S1, the infrared spectrum of the ligand HL1 exhibited a broad characteristic band at ca. 3438 cm−1 and can be attributed to the characteristic band of the νOH group. This band is weakened in the IR spectrum of the CuII complex, which is indicative of the fact that the phenolic OH groups of the ligand H2L2 have been deprotonated and coordinated to the CuII ions [59,60]. The ligand HL1 showed a characteristic C=N stretching band at ca. 1615 cm−1, while the C=N stretching band of the CuII complex appeared at ca. 1609 cm−1 [61]. In addition, the ligand HL1 exhibited typical aromatic C=C skeleton vibration bands at ca. 1449 and 1470 cm−1 and appeared at ca. 1443 and 1507 cm−1 for the CuII complex [62]. Meanwhile, the free ligand HL1 exhibited an Ar–O stretching band at ca. 1214 cm−1 and that of the CuII complex appeared at ca. 1205 cm−1, meaning the Ar–O stretching vibration frequency had shifted to a lower frequency. It is indicated that the Cu–O bonds are formed between the CuII ions and the phenoxy atoms of the free ligand H2L2 [63].

3.2. UV–Vis Spectra

The UV–Vis absorption and titration spectra of HL1 and the CuII complex at room temperature are depicted in Figure 1. In the UV–Vis titration experiment (micro drop), an ethanol solution of the ligand HL1 was prepared at a concentration of 5.0 × 10−5 M, and an aqueous solution of Cu(OAc)2·H2O was prepared with distilled water at a concentration of 1.0 × 10−3 M.
Two typical absorption peaks of HL1 at ca. 266 and 324 nm were clearly observed. The two peaks can be attributed respectively to the π–π* transitions of the benzene ring and the oxime group [64,65]. When the concentration of the CuII ion increased gradually, the absorption peaks had evidently changed to 271 nm. Compared with the peak (266 nm) of the free ligand HL1, this absorption peak was red-shifted, and another absorption peak at 324 nm disappeared in the UV–Vis absorption spectrum of the CuII complex, which indicated that the oxime nitrogen atoms of the ligand H2L2 have coordinated to the CuII ions [14,16].
Meanwhile, a new absorption peak appeared at ca. 382 nm, which was attributed to the characteristic LMCT of salamo-like transition metal complexes [66,67]. When the amount of Cu2+ droplets was added to 1.0 equivalent, the absorption peak at 382 nm reached the maximum value and did not change. The titration spectral data indicated that the ratio of displacement reaction was 1:1 ([Cu2+]/[HL1]).

3.3. Crystal Structure Description

The CuII complex crystallized in the triclinic system, space group P-1, which clearly indicated that the structure of the resulting complex was an unexpected dinuclear CuII complex of salamo-like ligand H2L2, not an expected CuII complex of half-salamo-like ligand HL1. Here, the half-salamo-like ligand HL1 was converted to a salamo-like ligand H2L2. This phenomenon of oxime oxygen atom participating in coordination has not been previously reported in the literature [6,9,11,12,13] and may be due to the catalysis of the CuII ion upon coordination [16]. Compared with the previously reported M/L as 1:2 [68], 3:2 [69], and 2:2 [70] complexes, it consisted of two CuII ions and two wholly deprotonated (L2)2− units. The two CuII ions (Cu1 and Cu2) have different (N2O3 and N2O2) coordination environments. The CuII ion (Cu1) is penta-coordinated with the donor N2O2 atoms (N1, N2, O1, and O4) of the (L2)2− unit and one oxime oxygen atom (O6) from another deprotonated (L2)2− unit. The four donor atoms (N1, N2, O1, and O4) formed a base plane, and the dihedral angle of the N1–Cu1–O1 and O4–Cu1–N2 planes was at 2.09(3)°. The axial position was occupied by the oxime oxygen atom (O6); thus, the Cu1 ion possessed a slightly twisted square pyramidal geometry with the τ value τ = 0.004 (τ < 0.5) [15,61]. The distance of Cu1–O6 (2.508(2)) was considerably longer than the Cu–O and Cu–N bonds (Cu1–O1, 1.914(2); Cu1–O4, 1.921(2); Cu1–N1, 2.014(3) and Cu1–N2, 1.964(3)) in [Cu2(L2)2], indicating a weaker interaction. The lengthening of Cu1-O6 should be assigned to the involvement of O6 in a dimer bridge formation; similar elongation of the M–O bond has also been found in the dimer of [Cu2(L2)2] [71]. The CuII ion labelled as Cu2 shows a twisted square planar coordination sphere, being the donor atoms N3, N4, O5, and O8 provided by the deprotonated (L2)2− unit, and the dihedral angle of the N3–Cu2–O5 and O8–Cu2–N4 planes was about 10.29(3)°.
The crystal structure of the CuII complex and the coordination polyhedra of the CuII ions are depicted in Figure 2. Significant bond lengths and angles are summarized in Table 3.

3.4. Supramolecular Interactions and Hirshfeld Surface Analysis

In the crystal structure of the CuII complex, there were three intermolecular (C8−H8A···O1, C24−H24A···Cl5, and C25−H25A···O8) and one intramolecular (C24−H24A···O3) hydrogen bondings (see Table 4), which played a role in stabilizing the crystal structure of the CuII complex [72,73]. As a result, the CuII complex formed a self-assembled infinite two-dimensional supramolecular structure via intermolecular hydrogen bondings, as shown in Figure 3. In particular the chlorine atom (Cl5) of the ligand formed intermolecular hydrogen bondings, which gave rise to a supramolecular structure that differs from most of the salamo-like metal complexes previously reported. In fact, the latter always assembled supramolecular structures through the formation of intermolecular hydrogen bondings involving solvent molecules [22,30,35,36,37].
The intramolecular and intermolecular interactions of molecular crystal of the CuII complex were explored further by surface analysis using the Crystal Explorer program [14]. The interactions in molecular crystal can be clearly observed. In the Hirshfeld surface, the existence of strong interactions showed up as red spots [74], while the blue regions were related to weak contacts. The Hirshfeld surface analysis of the CuII complex is as depicted in Figure 4a–e.
The short-range interaction distribution of the CuII complex was calculated by Hirshfeld surface two-dimensional (2D) fingerprint [75]. The grey represented all regions of the fingerprint, and the blue region was used to quantify the interaction between molecules, as depicted in Figure 5. The proportions were as follows: C–H/H–C, O–H/H–O, H–H/ H–H, and Cl–H/H–Cl interactions, incorporating 8.4%, 6.8%, 14.7%, and 48.0%, respectively, of the total Hirshfeld surfaces for every molecule of the CuII complex. It was clear from the above results that the intermolecular forces on the whole surface of Hirshfeld mainly came from Cl–H/H–Cl interaction. This is different from the previously reported salamo-like complexes [55,56], as the main interaction between them was from H–H/H–H interaction. In the CuII complex, Cl–H/H–Cl was the main interaction, which was consistent with the formation of supramolecular structure.

3.5. Fluorescence Properties

The fluorescence properties of HL1 and the CuII complex were studied in ethanol solution (5.0 × 10−5 M) at room temperature at ca. 390 nm excitation wavelength, as shown in Figure 6. The strong fluorescence of the ligand HL1 at ca. 460 nm can be attributed to the π–π* transition. The fluorescence quenching of the CuII complex at 460 nm can be observed at the same excitation wavelength, indicating the strong coordination of CuII ions with nitrogen and oxygen atoms of the ligand H2L2 [76,77]. The binding affinity between CuII ions and HL1 was determined further by fluorescence titration. With the increase of CuII ions (c = 1.0 × 10−3 M), the fluorescence intensities decreased linearly. When the concentration of CuII ions increased to 1.0 equivalent, the fluorescence completely quenched and reached the end of titration. Through the determination of a job curve (illustration), it was found to be consistent with the titration result. Furthermore, according to the corrected Benesi–Hildebrand formula, the bonding constant of the CuII ions to the ligand HL1 calculated in the Supplementary Materials was estimated to be 5.09 × 1010 M−1 [37].

4. Conclusions

In this work, we have designed and synthesized an unprecedented dinuclear CuII complex [Cu2(L2)2], and a series of characterizations were made in detail. The crystal structure analysis of the CuII complex indicated that the penta-coordinated Cu1 ion possessed a slightly twisted square pyramidal geometry, and the tetra-coordinated Cu2 ion had a twisted square planar one. The CuII complex was self-assembled by intermolecular C–H···O hydrogen-bonding interactions to form a 2D layered supramolecular network. Interestingly, one oxime oxygen atom participated in the coordination reported previously in the salamo-like metal complexes. The CuII complex possessed the characteristic of fluorescence quenching.

Supplementary Materials

The following are available online at https://www.mdpi.com/2073-4352/9/12/607/s1, Figure S1: The infrared spectra of the ligand HL1 and the CuII complex.

Author Contributions

Y.-X.S. conceived of and designed the experiments; Y.-Q.P. and X.X. performed the experiments; Y.Z. analyzed the data; Y.-X.S. and Y.-Q.P. wrote the paper. Y.-X.S. contributed reagents/materials/analysis tools.

Funding

This work was supported by the National Natural Science Foundation of China (Grant No. 21761018), and the Program for Excellent Team of Scientific Research in Lanzhou Jiaotong University (Grant No. 201706).

Conflicts of Interest

The authors declare no competing financial interests.

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Crystals 09 00607 sch001 550
Scheme 1. Synthetic route to the half-salamo-like ligand HL1.
Scheme 1. Synthetic route to the half-salamo-like ligand HL1.
Crystals 09 00607 sch001
Crystals 09 00607 sch002 550
Scheme 2. Synthetic route to the CuII complex.
Scheme 2. Synthetic route to the CuII complex.
Crystals 09 00607 sch002
Crystals 09 00607 g001 550
Figure 1. (a) The UV–Vis spectra of HL1 (c = 5.0 × 10−5 M) and the CuII complex (c = 5.0 × 10−5 M). (b) UV–Vis spectral changes of HL1 upon addition of the CuII ion (CH3CH2OH, HL1 = 5.0 × 10−5 M, 0 ≤ [Cu2+]/[HL1] ≤ 1.2). The inset shows the plot of absorbance at 382 nm against the molar ratio of [Cu2+]/[HL1].
Figure 1. (a) The UV–Vis spectra of HL1 (c = 5.0 × 10−5 M) and the CuII complex (c = 5.0 × 10−5 M). (b) UV–Vis spectral changes of HL1 upon addition of the CuII ion (CH3CH2OH, HL1 = 5.0 × 10−5 M, 0 ≤ [Cu2+]/[HL1] ≤ 1.2). The inset shows the plot of absorbance at 382 nm against the molar ratio of [Cu2+]/[HL1].
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Crystals 09 00607 g002 550
Figure 2. (a) Crystal structure of the CuII complex. (b) Coordination polyhedra for the CuII ions.
Figure 2. (a) Crystal structure of the CuII complex. (b) Coordination polyhedra for the CuII ions.
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Crystals 09 00607 g003 550
Figure 3. (a) View of intramolecular hydrogen bonding of the CuII complex; (b) View of intermolecular hydrogen bondings of the CuII complex.
Figure 3. (a) View of intramolecular hydrogen bonding of the CuII complex; (b) View of intermolecular hydrogen bondings of the CuII complex.
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Figure 4. Hirshfeld surface analysis of the CuII complex: (a) Curvedness; (b) Shape-Index; (c) dnorm; (d) de; (e) di.
Figure 4. Hirshfeld surface analysis of the CuII complex: (a) Curvedness; (b) Shape-Index; (c) dnorm; (d) de; (e) di.
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Crystals 09 00607 g005 550
Figure 5. Fingerprint plot of the CuII complex: full and resolved into C–H, O–H, H–H, and Cl–H contacts exhibiting the percentages of contacts contributing to the total Hirshfeld surface area of the molecule.
Figure 5. Fingerprint plot of the CuII complex: full and resolved into C–H, O–H, H–H, and Cl–H contacts exhibiting the percentages of contacts contributing to the total Hirshfeld surface area of the molecule.
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Crystals 09 00607 g006a 550Crystals 09 00607 g006b 550
Figure 6. (a) Emission spectra of HL1 and the CuII complex (c = 5.0 × 10−5 M, λex = 390 nm, ex slit: 5.0 nm, em slit: 5.0 nm). (b) Fluorescence titration spectra of HL1 (c = 5.0 × 10−5 M) with CuII ions (c = 1.0 × 10−3 M, λex = 390 nm, ex slit: 5.0 nm, em slit: 5.0 nm).
Figure 6. (a) Emission spectra of HL1 and the CuII complex (c = 5.0 × 10−5 M, λex = 390 nm, ex slit: 5.0 nm, em slit: 5.0 nm). (b) Fluorescence titration spectra of HL1 (c = 5.0 × 10−5 M) with CuII ions (c = 1.0 × 10−3 M, λex = 390 nm, ex slit: 5.0 nm, em slit: 5.0 nm).
Crystals 09 00607 g006aCrystals 09 00607 g006b
Table
Table 1. Crystal data and structure parameters for the CuII complex.
Table 1. Crystal data and structure parameters for the CuII complex.
CompoundThe CuII Complex
Empirical formulaC32H20Cl8Cu2N4O8
Molecular weight, g·mol−1999.22
Temperature (K)273 K
Wavelength (Å)0.71073
ColorBrown
Crystal size, mm30.25 × 0.18 × 0.13
Crystal shapeParallelepiped
Crystal systemTriclinic
Space groupP-1
Unit cell dimension
a (Å)10.7507(5)
b (Å)13.5169(6)
c (Å)14.3611(6)
α (°)86.689(2)
β (°)68.572(2)
γ (°)67.681(2)
V (Å3)1789.15(14)
Z2
Dc (g cm−3)1.855
μ (mm−1)1.845
F(000)996
θ Range (°)3.024–27.186
Index ranges−13 ≤ h ≤ 13, −17 ≤ k ≤ 16, −18 ≤ l ≤ 17
Reflections collected17905
Completeness (%)97.0
Data/restraints/parameters7728/0/487
Final R1/wR2 [I > 2σ(I)]R1 = 0.0349, wR2 = 0.0919
Final R1/wR2 (all data)R1 = 0.0459, wR2 = 0.0969
∆ρmax/min (e·Å−3)0.381 and −0.337
R1 = Σ‖Fo| − |Fc‖/Σ|Fo|; wR2 = [Σw(Fo2 − Fc2)2/Σw(Fo2)2]1/2, w =1/[s2(Fo2) + (0.0330P)2 + 1.9700P], where P = (Fo2 + 2Fc2)/3; GOF = [Σw(Fo2 − Fc2)2/nobs − nparam)]1/2.
Table
Table 2. Main infrared data (cm−1) for the ligand HL1 and the CuII complex.
Table 2. Main infrared data (cm−1) for the ligand HL1 and the CuII complex.
Compoundν(O–H)ν(C=N)ν(Ar–O)ν(C=C)
HL13438161512141470, 1449
The CuII complex–160912051507, 1443
Table
Table 3. Significant bond lengths (Å) and angles (°) for the CuII complex.
Table 3. Significant bond lengths (Å) and angles (°) for the CuII complex.
BondLengthsBondLengths
Cu1–O11.914(2)Cu2–O51.923(2)
Cu1–O41.921(2)Cu2–O81.897(2)
Cu1–O62.508(2)Cu2–N31.958(3)
Cu1–N12.014(3)Cu2–N42.007(3)
Cu1–N21.964(3)
BondAnglesBondAngles
O1–Cu1–O484.20(10)O6–Cu1–N286.93(9)
O1–Cu1–O692.95(9)N1–Cu1–N298.06(12)
O1–Cu1–N188.86(11)O5–Cu2–O884.87(10)
O1–Cu1–N2173.03(11)O5–Cu2–N388.47(10)
O4–Cu1–O697.49(9)O5–Cu2–N4168.37(10)
O4–Cu1–N1172.79(11)O8–Cu2–N3172.25(10)
O4–Cu1–N288.91(10)O8–Cu2–N388.93(10)
O6–Cu1–N184.76(9)N3–Cu2–N498.30(11)
Table
Table 4. Putative hydrogen bonding interactions (Å, °) for the CuII complex.
Table 4. Putative hydrogen bonding interactions (Å, °) for the CuII complex.
D–H···Ad(H···A)d(D···A)∠DHASymmetry Code
C24−H24A···O32.513.234(5)131
C8−H8A···O12.523.488(5)173– x, 1 – y, 2 – z
C24−H24A···Cl52.713.427(4)132–1 + x, y, z
C25−H25A···O82.463.394(6)1631 – x, 1 – y, 1 – z

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Sun, Y.-X.; Pan, Y.-Q.; Xu, X.; Zhang, Y. Unprecedented Dinuclear CuII N,O-Donor Complex: Synthesis, Structural Characterization, Fluorescence Property, and Hirshfeld Analysis. Crystals 2019, 9, 607. https://doi.org/10.3390/cryst9120607

AMA Style

Sun Y-X, Pan Y-Q, Xu X, Zhang Y. Unprecedented Dinuclear CuII N,O-Donor Complex: Synthesis, Structural Characterization, Fluorescence Property, and Hirshfeld Analysis. Crystals. 2019; 9(12):607. https://doi.org/10.3390/cryst9120607

Chicago/Turabian Style

Sun, Yin-Xia, Ying-Qi Pan, Xin Xu, and Yang Zhang. 2019. "Unprecedented Dinuclear CuII N,O-Donor Complex: Synthesis, Structural Characterization, Fluorescence Property, and Hirshfeld Analysis" Crystals 9, no. 12: 607. https://doi.org/10.3390/cryst9120607

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