Molecular and electronic structures of copper-cuprizone and analogues

• A paramagnetic dinuclear copper(II) complex, [CuII(L−)Cl]2 (1) LH = (E)-1,2-diphenyl-2-(2-(pyridine-2-yl)hydrozono)ethanone, an analogue of mono-hydrazone cuprizone, was isolated.
• The single crystal X-ray structure of 1 was successfully determined.
• B3LYP/DFT and TD DFT calculations of 1 were reported.
• Unrestricted DFT calculations disclosed that bis-deprotonated NN-chelation, (cis or trans-2NN), is ∼3 × 103 kJ/mol higher in energy than the mono-deprotonated NO-chelation, (cis or trans-2NO) precluding the existence of so far reported 2NN products.

A paramagnetic dinuclear copper(II) complex, [CuII(L−)Cl]2 (1) while LH = (E)-1,2-diphenyl-2-(2-(pyridine-2-yl)hydrozono)ethanone, an analogue of mono-hydrazone cuprizone (LmcpzH2), was isolated and substantiated by spectra, single crystal X-ray structure determination, unrestricted density functional theory (DFT) calculations and inter alia. Magnetic susceptibility measurement and EPR spectra confirmed the triplet state of 1 above 30 K because of two paramagnetic copper(II) centers. Unrestricted DFT calculations on copper cuprizone species with doublet spin state established similar electronic features and disclosed that bis-deprotonated NN-chelation, [Cu(Lmcpz)2]2−, (cis or trans-2NN), is ∼3 × 103 kJ/mol higher in energy than the mono-deprotonated NO-chelation, Cu(LmcpzH)2, (cis or trans-2NO) precluding the existence of so far reported 2NN products. The calculations revealed that in all isomers, due to the mixing of dx2−y2 orbital with a ligand group orbital as in 1, 48–50% spin density is delocalized over the LmcpzH2 ligand. In fluid solution, 1 absorbs strongly at 527 nm due to LMCT elucidated by the time dependent (TD) DFT calculations and the excited LMCT state is fluorescent (λex = 375 nm; λem = 405, 426 nm; Φ = 0.014).

Molecular and electronic structures of [CuLCl]2 (1), (LH = (E)-1,2-diphenyl-2-(2-(pyridine-2-yl) hydrozono)ethanone) were reported and compared with that of isomeric copper cuprizone complex (cis/trans-2NO, 2NN, 2OO).Figure optionsDownload as PowerPoint slide