Luminescent Rhenium(I) Pyridyldiaminocarbene Complexes: Photophysics, Anion-Binding, and CO₂-Capturing Properties

Abstract

A series of luminescent isocyanorhenium(I) complexes with chelating acyclic diaminocarbene ligands (N^C) has been synthesized and characterized. Two of these carbene complexes have also been structurally characterized by X-ray crystallography. These complexes show blue-to-red phosphorescence, with the emission maxima not only considerably varied with a change in the number of ancillary isocyanide ligands but also extremely sensitive to the electronic and steric nature of the substituents on the acyclic diaminocarbene ligand. A detailed study with the support of density functional theory calculations revealed that the lowest-energy absorption and phosphorescence of these complexes in a degassed CH2Cl2 solution are derived from the predominantly metal-to-ligand charge-transfer [dπ(Re) → π*(N^C)] excited state. The unprecedented anion-binding and CO2-capturing properties of the acyclic diaminocarbene have also been described.

Recent progress on NHC-stabilized early transition metal (group 3–7) complexes: Synthesis and applications

“…184,185 The molecular diversity of this family has been developed by varying the substituents and the nature of NHC ring: some recent examples are displayed in Figure 16 (complexes 173-175). 186,187,188,189,190 Overall, ligand structure/ photophysical properties correlations could be established thus allowing a fine-tuning of these properties. In 2020, Mauro and collaborators described a novel class of tricarbonyl Re(I) complexes bearing a pyridyl pyrido-annelated NHC as a chromophoric ligand, such as 174, which displayed a stable and long-lived, ligand-centered, red phosphorescence.…”

“…Interestingly and surprisingly, the presence of the NHC ligands attenuate their luminescent properties. 209 Finally, Various rhenium (V or VII) NHC complexes have been prepared, including water stable or 188 Re radiolabeled species. 210,211,212,213 In total, 10 technetium NHC complexes have been characterized by X-ray diffraction studies and the bond distances range from 2.07 to 2.23 Å.…”

Aerobically stable and substitutionally labile α-diimine rhenium dicarbonyl complexes

“…In the last decade the groups of Ko and Ishitani have introduced tunable isocyano and acetonitrile rhenium(I) diimine luminophores of general formula cis,cis-[Re(CO) 2 (N_N)(CNR) 2 ] + and cis,cis-and cis-trans-[Re(CO) 2 (-L 0/00 ) 2 (N_N)] + (with L 0 ¼ CH 3 CN and L 00 ¼ CH 3 CN, py, PR 3 or halide). 7,[20][21][22][23][24][25] Complexes are prepared by photo-substitutions/ decarbonylation of fac-[Re(CO) 3 (CNR) 2 Br] in the presence of diimine ligands (N_N) with broadband or UV excitation. N_N isonitrile analogues of the Kromer complexes were similarly obtained by photolytic decarbonylation of fac-[Re(CO) 3 (-N_N)(CNR)] + in the presence of CNR.…”

Aerobically Stable and Substitutionally Labile α-Diimine Rhenium Dicarbonyl Complexes

“…In the last decade the groups of Ko and Ishitani have introduced tunable isocyano and acetonitrile rhenium(I) diimine luminophores of general formula cis,cis-[Re(CO) 2 (N_N)(CNR) 2 ] + and cis,cisand cis-trans-[Re(CO) 2 (L' / '') 2 (N_N)] + (with L' = CH 3 CN and L'' = CH 3 CN, py, PR 3 or halide). 7,[20][21][22][23][24][25] Complexes are prepared by photosubstitutions/decarbonylation of fac-[Re(CO) 3 (CNR) 2 Br] in the presence of diimine ligands (N_N) with broadband or UV Please do not adjust margins excitation. N_N isonitrile analogues of the Kromer complexes were similarly obtained by photolytic decarbonylation of fac-[Re(CO) 3 (N_N)(CNR)] + in the presence of CNR.…”