Syntheses, crystal structures, and spectroscopic properties of two ion-pair charge transfer compounds containing bis(maleonitriledithiolato) platinum/palladium(II) anion and substituted benzylpyridinium

Two ion-pair charge-transfer compounds, [CNBzNH₂Py] ₂[M(mnt)₂]MeCN (CNBzNH₂Py⁺ = 1-(4'-cyanobenzyl)-4-aminopyridinium; mnt2-= maleonitriledithiolate; M=Pt (1), Pd (2)), have been synthesized and characterized. The X-ray single-crystal studies revealed that both of the crystals crystallize in the monoclinic space group P2_1/c with an asymmetric unit containing one [CNBzNH ₂Py]⁺ cation and a half of the [M(mnt)₂] ^2- anion together with one MeCN molecular; there is no evident change of the crystal system, and the dihedral angles between the phenyl and pyridine rings and the N3/C10/C11 reference plane of the cation, as well as the stacking modes of the anions and the cations, when the metal ion is changed from Pt(II) to Pd(II). There exist ππ interactions between the neighboring benzene ring and CN group of the cations, as well as H-bonding interactions between the CN group of the MeCN molecular and the NH₂ group of the cation in both of the compounds. Ultraviolet/visible (UV-vis) spectrum studies disclosed that these show different absorption bands in the UV-vis regions.