Determination of Geometries of some complexes of Ni(II), Cu(II)

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Template reactions play a very important role in the formation of many natural macro- heterocyclic compounds that have biological activities such as porphyrine, metalloenzyme etc. and become one type of the most important reactions in bioinorganic Chemistry and other relating fields.

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Nội dung Text: Determination of Geometries of some complexes of Ni(II), Cu(II)

Journal of Chemistry, Vol. 44 (4), P. 505 - 509, 2006 Determination of Geometries of some complexes of Ni(II), Cu(II) Received 5 July 2005 Vu Van Van, Nguyen Thanh Cuong, Le Kim Long, Lam Ngoc Thiem, Vu Dang Do Faculty of Chemistry, College of Natural Sciences, Vietnam National University of Hanoi Summary Calculations with 8 complexes of Cu(II) and Ni(II) with thiosemicarbazone bis(salicylaldehyde) were done within HyperChem 7.02 sotfware. The structure of complexes was determined. The UV-VIS spectra, single point of complexes were calculated and compared with experimental data. The calculated results have been confirmed by experimental structure of complexes. I - Introduction relating fields. In the early 1970’s, some Russian chemists Template reactions play a very important found a novel type of template reactions role in the formation of many natural macro- between thiosemicarbazone salicylaldehyde (1) heterocyclic compounds that have biological and salicylaldehyde (2) and the metal ions such activities such as porphyrine, metalloenzyme as Ni2+, Cu2+ (figure 1) [1]. It is necessary to etc. and become one type of the most important note that the condensation of 1 and 2 can not reactions in bioinorganic Chemistry and other occur without metal ions. - S S M = Ni2+, Cu2+, VO2+,. . . N NH N N N NH2 OH- M M O -H2O O O OH HO M(thsasal) anion 1 2 Figure 1: Template reaction The products of these reactions were studied of such products by quantum chemistry by methods of element analysis, conductivity calculations are given. It mainly deals with measurement, and magnetic moment measure- electronic spectra and geometry of the ment ... but the data were relatively modest. It is complexes formed in the template reaction experimentally studied the structure of the (figure 2). products by modern spectroscopic methods such as IR, UV-Vis, MS and NMR to examine the II - Calculation Methods proposed mechanism of the reaction [3]. In this paper, some more data obtained about structure The calculations have been done within the 505 software HyperChem 7.02 using semi-empirical carried out by ZINDO/S. Configuration Interac- methods. Calculations, which involve molecules tion (CI)-Singlely Excited method is chosen to containning transition metals, are only done calculate the electronic spectrum with both two well with ZINDO/1 and ZINDO/S [4]. choices: Orbital criterion (the numbers of All molecules (3-10) are built, geometrically occupy orbital and unoccupy orbital) and energy optimized by ZINDO/1 with convergence limit criterion (energy excited). Since orbital-crite- =10-5. All of algorithms have been tried. Only rion takes longer time and is not stable [4], only Conjugate Direction algorithm is able to give Energy Criterion is used. The maximum chosen the good geometry but it requires quite long energy has been varied to find the suitable one. calculating time. The other algorithms get Complexes with R = Na, K, NH4 are results fast but with not fine geometry. electrolytically dissociated [1, 2], so they can be With the optimized geometry, the Single considered as M (thsasal) anion. However, when Point and IR Spectrum computation have been M are Ni (II), Cu (II) situation is quite different. S R M R Complex M R Complex N N N M Na 3 K 9 Cu O O K 4 CH3 10 Ni NH4 5 H 6 Figure 2: Complexes formed in CH3 7 template reaction of 1 and 2 CH3CO 8 III - Results and Discussion Ni, Cu) are adequate in each complex (1-9 and 1-21 bonds, 1-10 and 1-13 bonds) and change 1. Geometry of complexes inconsiderable in different complexes. The bond angles of N-M-O are also adequate in The data of geometrically optimized complexes but the O-M-O bond angle is greater complexes of Ni(II) and Cu(II) (figure 3) are than the N-M-N bond angle in each complex. listed in table 1. The Ni, Cu complexes usually This is due to the strain of the ring MNNCN. have square planar or tetrahedron structure. The Both two-bond angles are almost the same in six torsion angles (table 1) in each complex different complexes. These things show the have approximate zero value and almost good optimized result and the suitable unchange from this complex to other complex. optimization method. Perhaps, the structures of This confirms the planar structures of complexes have conjugate- electrons, so complexes. optimization Conjugated Direction algorithm The lengths of M-N and M-O bonds (M = gave the best result. Figure 3: Optimized Geometry of 6 506 Table 1: Bond length and angle of geometrically optimized complexes Atoms Ni(thsasal)- 6 7 8 Cu(thsasal)- 10 Bond length () 1-9 1.827 1.819 1.826 1.826 1.830 1.821 1-21 1.841 1.835 1.843 1.837 1.844 1.837 1-10 1.923 1.922 1.927 1.920 1.921 1.920 1-13 1.910 1.920 1.921 1.932 1.912 1.919 Bond angle, O 9-1-10 96.13 95.60 95.13 94.73 95.53 95.43 13-1-21 95.30 94.54 93.61 94.95 94.89 94.07 9-1-21 86.77 87.43 89.38 87.96 87.53 88.15 10-1-13 81.80 82.43 81.88 82.34 82.05 82.35 Torsion angle × 103, O 8-10-1-9 1.68 -1.08 1.98 -6.65 63.96 -2.04 6-9-1-10 0.96 1.52 -7.19 2.18 7.39 12.39 11-10-1-13 0.19 1.16 0.49 -18.22 40.89 0.02 12-13-1-10 -0.91 -1.76 5.02 26.64 -29.72 0.02 14-13-1-21 -4.68 0.60 3.49 23.72 56.86 9.98 16-21-1-13 12.52 7.56 1.29 -24.04 0.53 9.76 Charge densities of atoms H27 and H28 are relative strength as following: lonepair > CH3 > listed in table 2 in order to find some relativity H. The increase of charge on H27 from 4 to 8 is with the chemical shifs of these atoms. Only the agree with the electron supplies of the groups 1 H-NMR spectra of 4 - 8 were recorded. It is bind to S atom. However, the increase of charge impossible to recorded the spectra of 9 and 10 on H28 from 4 to 8 is strange. because of magnetic field caused by the The order of chemical shifts is suitable with unpaired electron of Cu(II). the charge on the atoms H27 and H28 respectively, except 6. Table 2: Charge (calculated) and Chemical shifts (experimental) on H27 and H28 Calculated chemical shift 1H-NMR spectra gave the results which suite with experimental H27 H28 spectra. So ZINDO/1 is a good method for Complexes Charge Charge, , optimization and calculations. (e) , ppm e ppm The planar structure of complexes and the 4, 5 0.044 8.04 0.075 9.11 ZINDO optimized method are proved by the comparison between experimental UV-Vis 7 0.053 8.29 0.057 8.51 spectra with calculated UV-Vis spectra and 6 0.054 7.80 0.056 9.30 density charge of H atoms in the following part. 8 0.061 9.23 0.049 8.24 2. Electronic Spectra of complexes CH3CO are electrophile group while The electronic spectra of complexes were lonepair, CH3 and H are nucleophile groups with calculated with Criterion energy = 6 eV, 8 eV, 507 10 eV. However, energy of 6 eV is not enough 10 eV gives complicated results. Therefore, we for electrons in Ni(II) complexes transfer from used Criterion Energy 8 eV spectral results to ground state to excited state. Calculation with discuss. Figure 4: UV-Vis spectra of 6, experimental and calculated Table 3: Experimental UV-Vis spectra of Ni(II) complexes - (nm) Complexes 1 2 3 4 5 6 7 3 235 301 340 370 476 4 237 301 340 368 Shoulders 475 5 238 302 341 367 or bands 472 Weak overlapped bands at 6 238 302 340 368 by bands 471 ~530 nm 7 241 301 325 397 4 485 8 241 315 382 527 Inside Ligand 1 A1g 1 Eg 1 A1g 1 B2 g 1 A1 g 1 Eg Transfer CT d- For each central ion (Ni(II), Cu(II)), the with weak intensities (almost coincide with the UV-Vis spectra of all the complexes are almost background). the same. Calculated spectra (Ni(II) and Cu(II) complexes) are similar to experimental spectra I d xy (b2 g ) d x 2 y 2 (b1g ) ~ 1A1g 1 A2 g (figure 3). II d z 2 (a1g ) d x 2 y 2 (b1g ) ~ 1A1g 1B 1g According to Ligand Field Theory and Group Theory, square planar complexes of III d xz , d yz (e g ) d x 2 y 2 (b1g ) ~ 1A1g 1 Eg Ni(II) exhibit three d-d bands in range 400 - 600 nm. These bands are geometrically forbidden, N N so that their intensities are very weak. Both calculated and experimental spectra of 3 - 8 Ni bands have three bands in range 400 - 600 nm O O 508 Thus, 3 - 8 can be assigned to have square atoms are almost similar to these O atoms. planar conformation, and their spectra can be Thus, the four donor atoms are quite identical; assigned as in table 2. and again is the square planar structure proved. Table 4: Experimental UV-Vis spectra of Cu(II) IV - Conclusion complexes - (nm) From the calculated results and Complexes 1 2 3 4 5 experimental results, conclusion can be made that the geometries of transition metal M(Ni,Cu) 9 227 252 312 348 430 complexes with thiosemicarbazone are planar. 10 239 287 315 344 448 The ZINDO/1 and ZINDO/s methods are 2 2 suitable for transition metal complexes Inside Ligand B1g A1g CT calculations. Transfer References The Ligand Field Theory and Group Theory also affirm that there is only one d-d band at 1. . . , . . . about 400 - 600 nm in spectra of square planar , 16, 4 (1971). Cu(II) complexes. This band lies far from other 2. H. B. Gray, C. J. Ballhausen. J. Chem. Soc., bands and are symmetric. In fact, there is a 85, 260 - 265 (1963). symmetrical band at about 430 - 450 nm in both experimental and calculated spectra of each of 3. Vu Van Van. Vu Dang Do, Chu Dinh Kinh. Cu(II) complexes. Thus, 9 and 10 are square Advanced in Natural Science, In press. planar. 4. Hyperchem Release 7. Tools for molecular The atoms N10 and N13 are sp2 hybrided modeling. Copyright @2002 Hypercube while the atom O9 and O21 are sp3 hybrided. Inc, USA. The sp2 hybridation make the electronegative 5. Dang Ung Van, Vuong Minh Chau. Journal higher and the atom’s radius smaller than those of Analytical Sciences (Vietnamese). Vol. 7, in sp3 hybridation. This shows that these N No. 1, 53 - 58 (2002). 509