КООРДИНАЦИОННАЯ ХИМИЯ, 2009, том 35, № 1, с. 21-26
УДК 541.49
CRYSTAL STRUCTURE AND THEORETICAL CALCULATION OF COPPER COMPLEXES WITH 4,5-DIAZAFLUOREN-9-ONE
© 2009 R. L. Zhang1, J. S. Zhao1*, X. L. Xi2, P. Yang2, and Q. Z. Shi1
1Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry, Northwest University, Xi'an, 710069, P R. China
2Institute of Molecular Science, Chemical Biology and Molecular Engineering Laboratory of Education Ministry,
Shanxi University, Taiyuan 030006, P R. China
*E-mail: jszhao@nwu.edu.cn
Received October 9, 2007
Five copper complexes with 4,5-diazafluoren-9-one have been reported. Some of their structures are determined by single crystal X-ray diffraction. On the basis of the experimentation, all the complexes were calculated by DFT-B3LYP/LANL2DZ in Gaussian-98w. By analyzing the experimental and calculated values, it can be concluded, on the one hand, that the experimental results are proved thoroughly by the theoretical calculated results; on the other hand, the theoretical calculated results can deduce the experimental results reasonably.
INTRODUCTION EXPERIMENTAL
More recently, there has been an interest in the photochemical properties of copper complexes of phenanthro-line ligands as candidates for the development of photonic devices including sensors, photovoltaic devices, and switches [1]. The photochemical and electrochemical properties of the copper phenanthroline complexes have also been used to study their interaction with biological systems, in particular, DNA intercalation and scission [2, 3]. There have also been numerous studies of these types of complexes in relation to their biomimetic behavior [4]. 4,5-Diazafluoren-9-one (Dafo), which is a derivative of 1,10-phenanthroline, having an exocyclic keto function [5], has attracted attention of researchers due, perhaps, to its DNA intercalation [6], catalytic [7] and biological [8] properties. In order to synthesize supramolec-ular complexes possessing biological function and materials possessing catalysis and magnetism, our research team has analyzed many literature data in this field. Since 1999, we have synthesized a series of transition metal complexes of Dafo by various methods [9-13]. They have been characterized by element analysis, IR, UV, and flouo-rescene spectra. The crystal structures of some complexes are also measured. On the basis of the experimentation, DFT-B3LY /LANL2DZ in Gaussian-98w was used to optimize five copper complexes, and the subsequent calculation was continued. The energies of some frontier molecular orbitals, atomic net charge populations of these complexes were researched, and a reasonable structure of one complex was educed in theory.
Elemental analysis was performed on a Germany Vario EL ffl CHNOS analyzer. IR spectra were measured on a Germany EQUINO x 55 analyzer. Crystal structure was obtained on Bruker Smart-1000CCD and RigakuAFC7R diffractometers. The theoretical calculations were carried out with the Gaussian-98w package in the Window system on a Legend computer (256 Mb, 60 Gb). All reagents were of A.R. grade. Dafo was prepared following the literature method [11].
The syntheses of complexes
[Cu(Dafo)2(H2O)2](OPA)2 (OPA = o-phthalic acid, I), [Cu(Dafo)2(H2O)2](ClO4)2 (II), and
[Cu(Dafo)2(H2O)2](NO3)2 (III) are in the literature ([13], [9], and [10] for I, II, and III, respectively).
Synthesis of complex [Cu(Dafo)2Cl2] • 2H2O (IV). A solution of CuCl2 ■ 2H2O (0.340 g, 2.0 mmol) in 15 ml of water was dropped into a solution of ligand Dafo (0.362 g, 2.0 mmol) in 25 ml of water under stirring. After refluxing for 3 h, a few of crystals of CuCl2 ■ 2H2O (0.100 g) were added to the above solution. The reactants were refluxed for additional 10 h. Later, the reaction solution was left to stand for a day, and heavy green crystals formed. Then the crystals were filtered off, the filtrate was left to stand for 4 weeks, and column-like crystals suitable for X-ray diffraction were obtained. Melting point >300°C.
For C22H16Cl2CuN4O4
anal. calcd, %: C, 49.39; H, 2.99; N, 10.47.
Found, %: C, 48.79; H, 2.85; N, 10.26.
Synthesis of complex [Cu(Dafo)2Br2] (V). To a solution of Dafo (0.363 g, 0.002 mol) in 30 ml of acetone was added CuBr2 (0.345 g, 0.0015 mol) in a mixed solvent of 25 ml of acetone and 5 ml of water. A type of deep green precipitate formed immediately. The precipitate was filtered off, dried thoroughly in air, and the solid of complex V was obtained. Yield was 77.6%, melting point >300°C.
For C22Hi2Br2CuN4O2 anal. calcd, %: Found,%:
C, 44.59; H, 2.02; N, 9.46. C, 45.01; H, 1.85; N, 9.53.
Crystal structure determination and refinements.
The crystal structure analyses of complex I—III are depicted in detail in literature ([13], [9], and [10] for I, II, and III, respectively).
A single crystal of complex IV with dimensions 0.20 mm x 0.18 mm x 0.12 mm was selected for data collection, using a RigakuAFC7R diffractometer withgraph-ite monochromated MoA"a radiation (k = 0.71069 A). Data were collected by the rn-20 scan technique. The total reflections of 7047 were collected. Unique 2428 reflections could be observed and structure analysis was used (Riat = 0.0227). The structure was solved by direct methods. The positions of all non-H atoms were obtained from successive Fourier syntheses. The positions of all non-H atoms were refined anisotropically with full-matrix least-squares on F2. In the final difference map, the residuals are 0.592 and -0.449 e/A3, respectively. The crystallographic data and analysis parameters are showed as follows: mon-oclinic system, space group C2/c with cell dimensions: a = 7.2306(10), b = 15.364(2), c = 19.290(3) A, p = 98.938(3)°, V = 2116.9(5) A3, Z = 4, F(000) = 1084, M = 534.83, pcalcd = 1.678 g/cm3, p(Mo^a) = 1.003 mm-1, R = 0.0365, wR = 0.0509.
Calculation method. In the calculation, the geometry structures of complexes I-IV were constructed according to their crystal structures. The geometry structure of complexes V was constructed in Chem3D, and on the basis of this, a reasonable geometry structure was obtained by adjusting the ligand position. Density functional methods (DFT) is a very efficient method for research. In this paper, the five complexes were optimized and continued the subsequent calculation by DFT-B3LYP in Gaussian-98w. The transition metal copper was involved in all the calculation systems, so the effective basis set LANL2DZ was used in all the calculation systems.
RESULTS AND DISCUSSION
The crystal structures of complexes I-IV are shown in figure. The selected bond lengths and angles are listed in the Table 1.
The conclusion that in these complexes the copper atom is in a stretching octahedron can be summed up from the crystal structure data of the complexes. The reasons are probable as follows. 1) There is the Jahn-Teller effect in the copper complexes with Dafo. The orbital energy of
eg and t2g sets split into five initial degenerate d orbitals of the copper atom would give a corresponding change. On the one hand, the energy of eg splits due to the decrease in energy of the dz2 orbital. On the other hand, the energy of t2g splits due to the increase of energy of dy orbital. Consequently, the degeneracy of both eg and t2g orbilals is reduced. The interaction between one nitrogen atom of each Dafo and the central copper atom becomes very weak. Therefore, the stretching octahedron complexes of copper with Dafo are formed. 2) As Dafo itself is concerned, the large N-N bite distance (2.99 A) enforced by the rigid five-membered central ring leads to unequal binding by the two nitrogen atoms with copper [14]. 3) The steric effect of acid radicals and the reaction media perhaps influence the coordination of Dafo with copper.
By comparing with the coordination bond lengths of complexes I-IV, respectively, it is obvious that the interaction between one nitrogen atom of each Dafo and the copper atom is very weak. That is, in detail, the atoms of N(2), N(2A) in complex I, N(2), N(2A) in complex II, N(2), N(4) in complex III, and N(2), N(2A) in complex IV have the strong tendency of leaving the central atom. The fact complies with the above conclusion that in these complexes the copper atom is in a stretching octahedron.
Comparing complexes I-III with complex IV, we can say that the bond lengths of Cu-N(2) and Cu-N(2A) in complex I, Cu-N(2) and Cu-N(2A) in complex II, Cu-N(2) and Cu-N(4) in complex III are about 2.6 A, which is shorter than Cu-N(2) and Cu-N(2A) in complex IV (about 2.9 A). The main factor responsible for this behavior is that the coordinative ability of the oxygen atom is stronger than that of the chlorine atom, which results from the radius of the oxygen atom that is shorter than that of the chlorine atom and the electronic density of the former is higher than that of the latter.
Although the crystal of complex V was not obtained, its structure can be educed from the calculated results. This will be further discussed in this paper.
The data of selected bonds and angles for the optimized structures I-V are shown in Table 1 (the experimental data are in the brackets). Comparing with the experimental values of complexes I-IV, the average deviation of the calculated value and the experimental value of the main bond lengths and bond angles in the optimized structure is in the rang of 1-2% (very few exception). The reasons of the deviation may be as follows: the selecting calculation methods and the approximation of setup groups; the neglecting anionic effect in the course of calculation; the chemical environmental difference of the complex (calculation was based on gas geometry configuration). The deviation can be accepted in theoretical calculation for a big system.
Complexes IV and V are both copper complexes with Dafo and halogen, so their structures should be similar. The optimized structures of the two complexes are very close to each other; the calculated value of the main bon
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