Unique Solvatochromic Behavior of Unsymmetrical Platinum-Dithiolene Complexes Coordinated by 4,4'-Dinonyl-2,2'-Bipyridine

Unsymmetrical metal dithiolene complexes [(nonyl-bpy)Pt(dmit)] (1) and [(nonyl-bpy)Pt(C8H4S8)] (2) (nonyl-bpy=4,4-dinonyl-2,2-bypiridine, dmit=4,5-disulphanyl-1,3-dithiol-2-thionate(2-), C8H4S82-=2-{(4,5-ethylenedithio)-1,3-dithiole-2-ylidene}-1,3-dithiole-4,5-dithiolate(2-)) are synthesized in this study. For 1, two electronic absorption bands at approximately 466 and 584 nm in chloroform are observed and assigned to an intra-ligand pi-pi* transition in the dmit moiety and an intramolecular-mixed metal/ligand-to-ligand charge transfer transition (LL'CT) from its highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO), respectively. Complex 2 exhibits two absorption bands at approximately 450 and 676 nm in chloroform. Both bands correspond to LL'CT from HOMO-1 to LUMO and HOMO to LUMO. With increasing solvent polarity, the absorption bands from the HOMO-LUMO transitions for 1 and 2 shift hypsochromically. Conversely, the 1 and 2 absorption bands exhibit red and blue shifts, respectively.

Automated summary

Two unsymmetrical metal dithiolene complexes, labeled as 1 and 2, were synthesized and studied. The absorption bands of the HOMO-LUMO transitions for 1 and 2 shift in opposite directions with increasing solvent polarity, resulting in red and blue shifts, respectively.