Abstract
The crystal structure of the title compound, [Ru(C7H6N4)3](PF6)2·3H2O, a novel RuII complex with the bidentate ligand 2-(1H-imidazol-2-yl)pyrimidine, comprises a complex cation in the meridional form exclusively, with a distorted octa-hedral geometry about the ruthenium(II) cation. The Ru-N bonds involving imidazole N atoms are comparatively shorter than the Ru-N bonds from pyrimidine because of the stronger basicity of the imidazole moiety. The three-dimensional hydrogen-bonded network involves all species in the lattice with water mol-ecules inter-acting with both counter-ions and NH hydrogen atoms from the complex. The supra-molecular structure of the crystal also shows that two units of the complex bind strongly through a mutual N-H⋯N bond. The electronic absorption spectrum of the complex displays an asymmetric band at 421 nm, which might point to the presence of two metal-to-ligand charge-transfer (MLCT) bands. Electrochemical measurements show a quasi-reversible peak referring to the RuIII/RuII reduction at 0.87 V versus Ag/AgCl.
Highlights
The crystal structure of the title compound, [Ru(C7H6N4)3](PF6)2Á3H2O, a novel RuII complex with the bidentate ligand 2-(1H-imidazol-2-yl)pyrimidine, comprises a complex cation in the meridional form exclusively, with a distorted octahedral geometry about the ruthenium(II) cation
The electronic absorption spectrum of the complex displays an asymmetric band at 421 nm, which might point to the presence of two metal-to-ligand chargetransfer (MLCT) bands
An interesting class of asymmetric ligands are heteroaryl-imidazoles, since a combination of electron-rich and electron-poor rings can be used to tune the electronic properties of the final complexes (Ratier de Arruda et al, 2017; Nakahata et al, 2017)
Summary
Since the first preparation of the tris(2,2-bipyridine) ruthenium(II) complex by Burstall (1936), its interesting electrochemical and photochemical properties have stimulated the preparation and characterization of numerous analogous ruthenium(II) complexes (Le-Quang et al, 2018; Dong et al, 2018; Linares et al, 2013). An interesting class of asymmetric ligands are heteroaryl-imidazoles, since a combination of electron-rich and electron-poor rings can be used to tune the electronic properties of the final complexes (Ratier de Arruda et al, 2017; Nakahata et al, 2017). In this context, we have devised a synthetic procedure to obtain exclusively the meridional isomer of the first reported homoleptic RuII complex with the bidentate 2-(1H-imidazol2-yl)pyrimidine (impm) ligand containing imidazole (im) and pyrimidine (pm) rings in the same unit. Value with Nim—Ru—Npm angles ranging from 78.5 (2) to 78.7 (2), the latter being the main cause for the distorted octahedral configuration
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