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Structural and electronic effects involving pyridine rings in 4-methylpyridine Cu4OX6L4 complexes. I. Vibrational spectra of Cu4OBr n Cl(6−n)(4-Mepy)4 complexes

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Abstract

Gaussian analysis of bands between 500 cm−1 and 600 cm−1 attributed to the \( \tilde \nu \) as (Cu4O) stretching vibration of the tetrahedral Cu4O core in Cu4OBr n Cl(6−n)(4-Mepy)4 (n = 0–6) complexes showed two bands, symmetry reduction of the T 2 mode of vibration towards the A 1 and E modes and vibrational coupling with an R-sensitive in-plane pyridine ring bending. The Cu-O bond is considered as vibrationally coupled with the Cu-N bond and the pyridine ring through the donor-acceptor vibrational coupling and the corresponding equilibrium charge distribution. The linear correlation between \( \tilde \nu \) as(Cu4O) and the number of bromides in Cu4OBr n Cl(6−n)(4-Mepy)4 complexes was used for the estimation of partial charges on the 4-Mepy ligands which were positive for the prevailing donors and negative for the prevailing acceptors thus evoking a π-back bonding between the Cu(II) atoms and the 4-Mepy ligands. Correlations involving selected bond lengths and bond angles in the molecular structure of the Cu4OCl6(4-Mepy)4 complex with four symmetrically independent molecules present in the unit cell indicate a symmetry reduction of the T 2 mode of vibration and the π-back bonding between the Cu(II) atoms and the 4-Mepy ligands.

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Ondrejovič, G., Koman, M. & Kotočová, A. Structural and electronic effects involving pyridine rings in 4-methylpyridine Cu4OX6L4 complexes. I. Vibrational spectra of Cu4OBr n Cl(6−n)(4-Mepy)4 complexes. Chem. Pap. 62, 480–486 (2008). https://doi.org/10.2478/s11696-008-0055-6

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  • DOI: https://doi.org/10.2478/s11696-008-0055-6

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