Linear nonanuclear chromium(II) complex with pyrazine-modulated pentapyridyltetraamine ligand: Synthesis, structure and properties
Journal
Journal of Molecular Structure
Journal Volume
1331
ISSN
0022-2860
Date Issued
2025-06
Author(s)
Rayyat Huseyn Ismayilov
Sabina Zahid Ismayilova
Dilgam Babir Tagiyev
Ajdar Akber Medjidov
Yasin Isa Jafarov
Wen-Zhen Wang
Chen-Yu Yeh
Su-Ying Chien
Gene-Hsiang Lee
Abstract
Through a new two-pyrazine-modulated oligo-α-pyridylamino ligand, N2,N2′-(pyridine-2,6-diyl)bis(N6-(pyrazin-2-yl)pyridine-2,6-diamine) (H4N9-2pz) (1), the highest nuclearity linear nonachromium(II) metal string complex [Cr9(µ9-N9-2pz)4Cl2] (2) was successfully synthesized and structurally characterized. According to X-ray crystallographic studies, the complex 2 showed a localized unsymmetrical structure consisting of four quadruple Cr–Cr bonds and one single high-spin Cr(II) at the end of the molecule. The four deprotonated supporting ligands are helically wrapped around the metal score. Temperature-dependent magnetic study revealed a quintet ground state resulting from the isolated, high-spin Cr(II) atom. Electrochemical studies reveal two reversible oxidation waves at E1/2 = +0.54 V and E1/2 = +0.85 V, indicating that the complex exhibits greater stability against oxidation compared to its one-pyrazine-modulated analogue [Cr9(μ9-N9-mpz)4Cl2], which shows a first oxidation peak at +0.38 V. This enhanced stability is attributed to the stronger electron-withdrawing nature of the two-pyrazine-modulated H4N9-2pz ligand. So, in spite of similar crystal structure and magnetic properties, the newly synthesized nonanuclear Cr(II) string is characterized by very different electrochemical properties and short Cr-axial ligand distances compared to its one-pyrazine-modulated analogue [Cr9(μ9-N9-mpz)4Cl2]. Overall, these findings highlight the critical role of the pyrazine-modulated ligand in enhancing the stability and electron structure of nonachromium string complexes, paving the way for designing more stable and oxidation-resistant metal chains.
Subjects
Chain structure
Chromium
Modified N ligand
Multiple bond
X-ray diffraction
SDGs
Publisher
Elsevier BV
Type
journal article