Spectroscopic and luminescence studies on square-planar platinum(II) complexes with anionic tridentate 3-bis(2-pyridylimino)isoindoline derivatives.
Reactions of 1,3-bis(2-pyridylimino)isoindoline (HL1), 1,3-bis(2-pyridylimino)benz(f)isoindoline (HL2), or 5,6-dihydro-2,3-diphenyl-5-(pyridin-2-ylimino)pyrrolo[3,4-b]pyrazin-7-ylidene)pyridin-2-amine (HL3) with Pt(tht)(2)Cl(2) (tht = tetrahydrothiophene) afforded the corresponding Pt(L)Cl complexes. A series of neutral platinum(II) alkynyl complexes Pt(L)(C[triple bond]CR) were prepared by reactions of the precursors Pt(L)Cl with alkynyl ligands through CuI-catalyzed platinum acetylide sigma coordination. Crystal structural determination of Pt(L3)Cl (3), Pt(L1)(C[triple bond]CPh) (4), and Pt(L1)(C[triple bond]CC(6)H(4)Bu(t)-4) (6) by X-ray crystallography revealed that the neutral platinum(Pi) complexes with monoanionic tridentate L ligands display more perfect square-planar geometry than that in platinum(II) complexes with neutral tridentate 2,2':6',2''-terpyridyl ligands. Both the Pt(L)Cl and Pt(L)(C[triple bond]CC(6)H(4)R-4) complexes exhibit low-energy absorption at 400-550 nm, arising primarily from pi --> pi*(L) intraligand (IL) and 5d(Pt) --> pi*(L) metal-to-ligand charge-transfer (MLCT) transitions as suggested from density functional theory calculations. They display bright-orange to red room-temperature luminescence in fluid dichloromethane solutions with microsecond to submicrosecond ranges of emissive lifetimes and 0.03-3.79% quantum yields, originating mainly from (3)IL and (3)MLCT excited states. Compared with the emissive state in Pt(L)Cl complexes, substitution of the coordinated Cl with C[triple bond]CC(6)H(4)R-4 in Pt(L)(C[triple bond]CC(6)H(4)R-4) complexes induces an obviously enhanced contribution from the (3)[pi(C[triple bond]CC(6)H(4)R-4) --> pi*(L)] ligand-to-ligand charge-transfer (LLCT) triplet state. The photophysical properties can be finely tuned by modifying both the L and alkynyl ligands. The calculated absorption and emission spectra in dichloromethane coincide well with those measured in a fluid dichloromethane solution at ambient temperature.
Wen
Hui-Min
HM
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter and Graduate School of CAS, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China.
Wu
Yu-Hui
YH
Fan
Yang
Y
Zhang
Li-Yi
LY
Chen
Chang-Neng
CN
Chen
Zhong-Ning
ZN