Crowded Cu(I) Complexes Involving Benzo[h]quinoline:  π-Stacking Effects and Long-Lived Excited States

Abstract

The Friedländer condensation was employed to synthesize two series of 3,3'-polymethylene bridged ligands, L, based on 2-(2'-pyridyl)-benzo[h]quinoline and 2,2'-bibenzo[h]quinoline (BHQ) along with the fully aromatic naphtho[1,2-b]-1,10-phenanthroline. Complexes [Cu(L)(2)](+) were prepared as their perchlorate or hexafluorophosphate salts. The solution state structures were analyzed by NMR and shielding effects reflected significant interligand pi-stacking interaction in the complexes. Solid-state structures of the complexes where L = 3,3'-tetramethylene-2,2'-bibenzo[h]quinoline or naphtho[1,2-b]-1,10-phenanthroline were determined by X-ray analysis. The tetramethylene bridged complex showed a highly distorted coordination geometry with the BHQ rings of opposing ligands pi-stacked at a interplanar distance of about 3.37 A. Complexes of the BHQ series showed a pronounced MLCT absorption maximum which shifted bathochromically from 496 to 610 nm as the 3,3'-bridge decreased from 4 to 2 carbons. The BHQ complexes luminesced strongly in CH(2)Cl(2) solution and the tetramethylene-bridged system showed the longest yet recorded excited-state lifetime for a copper MLCT excited state, tau = 5.3 micros and Phi = 0.10.

Synthesis, Structures, and Unique Luminescent Properties of Tridentate C∧C∧N Cyclometalated Complexes of Iridium

“…This is a similar result to that reported in a literature, [18] although another recent report showed a significant effect on the luminescent properties. [19] The lu- Figure 4. Photoluminescence spectra (1.0 ϫ 10 -5 m in CH 2 Cl 2 ) for 9, 10, 11, 12, and 14, for which the irradiated wavelengths were 400 nm.…”

Light to Hydrogen: Photocatalytic Hydrogen Generation from Water with Molecularly-Defined Iron Complexes

“…Taking this into consideration, significantly improved quantum yields of up to 48% at a wavelength of 415 nm and 41% at 440 nm, respectively, were achieved (Figure 2 [154] and at the same time favor the tetrahedral (Td) geometry. Thus, in the MLCT exited state, the flattening to the preferred square planar geometry is significantly reduced [155,156]. A number of molecularly-defined Cu-PS has been synthesized based on various combinations of bidentate phosphines and amines.…”

Spectroscopic and electrochemical properties of heteroleptic cationic copper complexes bis-(diphenylphosphino)alkane-(2,2′-biquinoline)copper(I). Crystal structure of bis(diphenylphosphino)ethane-(2,2′-biquinoline)copper(I) perchlorate

“…The geometry of copper(I) complexes may also be modulated by ligands allowing a less restricted way of coordination around the metal center and potential distortion of the tetrahedral arrangement [3,7].…”