One-dimensional metal-bis-dithiolene compounds with diverse ion-pair arrangements, various magnetic properties and intense near-infrared absorption

Five one-dimensional (1D) ion-pair compounds [4′-R-Bz-NH2Py][M(mnt)2] (mnt2− = maleonitriledithiolate, 4′-R-Bz-NH2Py+ = 1-(4′-R-benzyl)-4-aminopyridinium and M = Pt, R = F (1), Br (2), I (3), CF3 (4); M = Ni, R = CF3 (5)) were investigated structurally and magnetically. Compounds 2 and 3 are isostructural; 4 and 5 are isomorphic. The magnetic [M(mnt)2]− anions form a 1D tetrameric stack in crystal 1, while dimeric stack in crystals 2–5. Compounds 1, 2 and 4 are diamagnetism over the temperature range 1.8–300 K, 3 shows a spin-Peierls-type transition around 124 K and 5 displays the typically magnetic character of a low-dimensional antiferromagnetic spin system with a broad maximum centered around 70 K. The attempts are failed to fit variable temperature magnetic susceptibility of both 3 in high-temperature phase and 5 over 1.8–350 K by an S = ½ Heisenberg dimer and 1D alternating chain models, probably due to anisotropic exchange interactions. Five compounds show a broad and intense near-IR absorption band in 750–1600 nm region.