Dinuclear Nickel(II) and Copper(II) Complexes of 8‐Quinoline‐1H‐pyrazole‐3‐carboxamide: Crystal Structure, Magnetic Properties, and DFT Calculations

Abstract

Homoleptic dinuclear complexes [M2(qpyzc)2] (M=Cu (1) or Ni (2) were obtained from the readily synthesised trischelate pyrazole‐based qpyzc ligand (H2qpyzc=8‐quinoline‐1H‐pyrazole‐3‐carboxamide). Their crystal and molecular structures, magnetic properties, and UV‐vis spectra were reported alongside with DFT and TD‐DFT calculations. Trigonality index τ’4 values of 0.25 and 0.21 for the Cu and Ni centres, respectively reveal a marked distortion from square planar geometry. The two metal coordination planes within a complex are tilted towards each other with 40.2(1)° for Cu(II) and 34.5(2)° for Ni(II). The central six‐membered M2N4 metallocycle is almost planar and the two anionic pyrazolate rings are tilted towards each other by 37.4(1)° (1) and 38.5(2)° (2), respectively. Regardless of this peculiar bonding situation magnetic measurements on 1 are in line with medium‐sized antiferromagnetic coupling with a coupling constant of J=−100 cm−1, an isotropic g value of 2.11 and an S=0 ground state. Complex 2 seems to be diamagnetic. DFT calculations gave an excellent agreement between calculated and experimental metrics of the complexes and supported the prevalence of the singlet ground state for 1. TD‐DFT calculated UV‐vis absorption spectra agree well with observed absorptions and the red colour of both compounds.

Recent developments in supramolecular complexes of azabenzenes containing one to four N atoms: synthetic strategies, structures, and magnetic properties

“…in 2021 reported an easy-to-synthesize small molecule quinoline-based ligand L12 and its dinuclear Cu II and Ni II complexes [Cu 2 (qpyzc) 2 ] ( CuL12) and [Ni 2 (qpyzc) 2 ] ( NiL12) respectively. 55 The ligand contained one coordination NNN pocket in which either of the metal ions could well-fit and the fourth coordination site was satisfied by the other N of pyrazole moiety from another complex. Both the complexes acquired a distorted square planner geometry and the overall charge of the complexes were balanced from the ligand only.…”

Hidrazon Türevi Yeni Fe(II), Co(II), Ni(II) ve Cu(II) Komplekslerinin Sentezi ve Karakterizasyonu

“…L-Cu kompleksi için kare düzlem [41] ve dinükleer yapı önerilmiştir. Dinükleer bakır kompleksleri incelendiğinde genellikle güçlü antiferromanyetik özellikte oldukları gözlemlenmiştir [42,43]. L-Ni için ölçülen değer oktahedral nikel kompleksleri için verilen değerler aralığından (2.8-3.2 BM) oldukça düşüktür [44].…”