عنوان المقالة:New diethoxo-bridged dinuclear Cr(III) complexes with derivatives of the quinoxaline-2,3-dione ligand and 2,20-bipyridine as a co-ligand: Syntheses, spectral characterizations, magnetic properties, antimicrobial inhibitory activities and interpretation of the electronic absorption spectra using the ZINDO/S-CI semi-empirical method
Attia S. Attia, Ayman A. Abdel Aziz, Khalifa A. Alfallous, M.F. El-Shahat
Abstract
Two new diethoxo-bridged dinuclear Cr(III) complexes, [Cr(QX)(bpy)EtO]2 [QX = 6,7-dichloroquinoxaline-
2,3-dione (1); 6,7-dimethylquinoxaline-2,3-dione (2)], have been synthesized and characterized.
The complexes were initially characterized on the basis of their elemental and mass analyses. The infrared
studies were useful in assigning the coordination mode of the quinoxaline-2,3-dione ligand to the
chromium metal. In addition, the presence of l-ethoxo bridges was inferred from the characteristic vibrational
bands in the IR spectra of both complexes. The structural and vibrational behaviors of both complexes
have been elucidated using a parameterized PM3 semi-empirical method. The magnetic
susceptibility, measured at 298 K, indicated exchange interactions between the two Cr(III) centers. The
observed effective magnetic moments have been correlated to the calculated Cr Cr distances and Cr–
O–Cr angles of the Cr(OEt)2Cr cores in both complexes. The ESR spectra have been recorded on powder
samples at 293 K. The dominant quintet state has been computer-simulated with the parameters
J = 23 cm1, g = 2.11, D = 0.074 cm1 and E = 0.008 cm1 for 1. On the other hand, the spectrum of complex
2, which showed two slightly different Cr centers, has been simulated with J = 17 cm1, g1 = 2.17,
D1 = 0.063 cm1, E1 = 0.012 cm1 for site 1 and g2 = 2.055, D2 = 0.065 cm1 and E2 = 0.0087 cm1 for site
2. The electronic spectra of the studied complexes were dominated by charge-transfer, [Cr(dp)?bpy(p⁄)
and QX(O-pp)?Cr(dp )], and spin-allowed d–d transitions. In addition, low-energy maxima characteristics
of the dinuclear transition metal complexes were observed in the 550–1050 nm region. Theoretical
studies of the electronic spectra by the ZINDO/S-CI method were useful in interpreting the observed electronic
transitions. The antimicrobial activity studies have indicated a significant inhibitory activity of
complex 2 against the studied bacteria and complex 1 showed the highest inhibitory activity against
the studied fungi.
خليفة عبدالسلام علي الفلوس | khalifa abdualsalam alfallous | 5178