Combined Experimental and Computational Study of Pyren-2,7-diyl-Bridged Diruthenium Complexes with Various Terminal Ligands

Cyclometalated diruthenium complexes 1(PF6)2–5(PF6)2 bridged by 1,3,6,8-tetra(pyrid-2-yl)-pyrene have been prepared, with the terminal ligand bis(N-methylbenzimidazolyl)pyridine (1(PF6)2), 4′-di-(p-methoxyphenyl)amino-2,2′:6′,2″-terpyridine (2(PF6)2), 4′-p-methoxyphenyl-2,2′:6′,2″-terpyridine (3(PF6)2), 2,2′:6′,2″-terpyridine (4(PF6)2), and trimethyl-4,4′,4″-tricarboxylate-2,2′:6′,2″-terpyridine (5(PF6)2). The single-crystal X-ray structure of 4(PF6)2 is presented. These complexes show two stepwise anodic redox pairs, and the potentials progressively increase from 1(PF6)2 to 5(PF6)2. Complexes 1(PF6)2–4(PF6)2 have comparable electrochemical potential splitting of 200–210 mV, while complex 5(PF6)2 has a splitting of 170 mV. Upon one-electron oxidation by chemical oxidation or electrolysis, the resulting mixed-valent complexes 13+–53+ display broad and intense absorptions between 1000 and 3000 nm. Complexes 13+ and 23+ show the presence of a higher-energy shoulder band in addition to the main near-infrared ...