Dual Emission from Rhenium(I) Complexes Induced by an Interligand Aromatic Interaction

Abstract

A series of rhenium(I) diimine complexes cis,trans-[Re(dmb)(CO)(2)(PR(1)R(2)R(3))(PR(4)R(5)R(6))](+) (dmb=4,4'-dimethyl-2,2'-bipyridine, R(n)=phenyl or alkyl), each of which bears two phosphine ligands with various numbers of phenyl groups, has been synthesized by using the photochemical ligand-substitution reaction. Detailed studies of the structural features, not only in the crystal but also in solution, indicate that the number of phenyl groups is a crucial factor in controlling the rotational conformation of the phosphine ligands, which in turn determines the extent of the π-π interaction between the aromatic diimine ligand and the phenyl group(s). The π-π interaction strongly affected both electrochemical and photophysical properties: 1) the oxidation power of the Re complex became stronger, 2) the lifetime of the excited state became longer, and 3) the Stokes shift between the (1) MLCT absorption band and emission from the corresponding (3) MLCT excited state became smaller. In particular, the diphenyl and triphenyl phosphine had much greater influence on the properties than the monophenyl phosphine ligand. Dual emission was observed from the different rotational conformers of the complexes with an intermediate number of phenyl groups in the phosphine ligands.

A Rare Type of Rhenium(I) Diimine Complexes with Unsupported Coordinated Phosphine Oxide Ligands: Synthesis, Structural Characterization, Photophysical and Theoretical Study

“…In dichloromethane solution all compounds display yellow to orange 3 MLCT [π*(N–N)→dπ(Re)] phosphorescence with structureless emission bands (Figure ) and lifetimes in the range 0.5–0.7 µs in degassed solution (Table ). The assignment of the phosphorescence to 3 MLCT (where M implies rhenium tricarbonyl motif) excited state is also supported by DFT calculations (Figure , Figure S14, Table S6) and is in complete agreement with the experimental results and theoretical analysis of closely analogous systems studied earlier . It is also well‐known, that insertion of electron‐donating substituents into coordinated diimine ligand leds to a hypsochromic shift of the emission maximum, and this trend is clearly observed for the complexes under study.…”

Fluorescence probes for prokaryotic and eukaryotic cells using Re(CO)3+complexes with an electron withdrawing ancillary ligand

“…These results present similar values than those published by different authors using analogous complexes [72][73][74][75][76][77][78][79][80][81]. Interphase: Pt|1.C1, rhenium oxidations appear at E p 1.51 V, which seems to be electrochemically irreversible, and a second of reversible character at E ½ 1.90 V. On the other hand C2 presents same peaks at E p 1.46 V and E ½ 1.86 V, respectively.…”

Experimental and theoretical studies of the ancillary ligand (E)-2-((3-amino-pyridin-4-ylimino)-methyl)-4,6-di-tert-butylphenol in the rhenium(i) core

“…S9, ESI †), and showed an irreversible process with only oxidative peak potential, according to analogous complexes. [43][44][45][46] Computational optimizations of the oxidized and reduced states of the studied compounds, deeb, C1 and C2, were performed. In this sense, this process occurs at higher potentials relative to C1, which means that L has an electron-withdrawing effect over the positive charge on the rhenium atom.…”