Issue 40, 2024

Structural and electrochemical properties of mononuclear copper(ii) complexes with pentadentate ethylenediamine-based ligands with pyridine/quinoline/isoquinoline/quinoxaline binding sites

Abstract

N-Monosubstituted ethylenediamine derivatives with three methylene-tethered aromatic groups ((ArCH2)2NCH2CH2N(R)CH2Ar (R-ArArAr), where Ar = 2-pyridyl, 2-quinolyl, 1- and 3-isoquinolyl and 2-quinoxalyl; R = methyl, benzyl and phenyl) were utilized as pentadentate ligands for copper(II) complexation. Fifteen mononuclear copper(II) complexes were synthesized and exhibit differences in cyclic voltammetry, absorption spectroscopy and solid state geometries, depending on the aromatic group (Ar) and the substituent on the aliphatic nitrogen atom (R) of the ligand. Compared with the pyridine and isoquinoline complexes, the quinoline and quinoxaline derivatives exhibit distinct Cu(II)/Cu(I) redox potentials and d–d transition absorption wavelengths. Similarly, the phenyl derivatives are different from their methyl and benzyl counterparts. These characteristic trends are discussed in relation to the square-pyramidal/trigonal–bipyramidal structure of the complexes which is perturbed by the location of quinoline moieties in the penta- or hexacoordinate complexes with Jahn–Teller distortion. In addition, the results are compared to the copper(II) complexes with pyridine/quinoline mixed ligands, Ph-Ar1Ar2Ar3 ((Ar1CH2)(Ar2CH2)NCH2CH2N(Ph)CH2Ar3).

Graphical abstract: Structural and electrochemical properties of mononuclear copper(ii) complexes with pentadentate ethylenediamine-based ligands with pyridine/quinoline/isoquinoline/quinoxaline binding sites

Supplementary files

Article information

Article type
Paper
Submitted
20 Aug 2024
Accepted
23 Sep 2024
First published
24 Sep 2024

Dalton Trans., 2024,53, 16716-16732

Structural and electrochemical properties of mononuclear copper(II) complexes with pentadentate ethylenediamine-based ligands with pyridine/quinoline/isoquinoline/quinoxaline binding sites

Y. Mikata, M. Akedo, E. Hamamoto, S. Yoshida, S. Shoji, Y. Ohsedo, T. Matsuo, T. Storr and Y. Funahashi, Dalton Trans., 2024, 53, 16716 DOI: 10.1039/D4DT02363C

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