Ruthenium(II) σ-Acetylide and Carbene Complexes Supported by the Terpyridine−Bipyridine Ligand Set:  Structural, Spectroscopic, and Photochemical Studies

Abstract

A series of acetylide-and carbene-ruthenium complexes containing polypyridine ligands, [(tpy)(bpy)RuCtCR] + (tpy ) 2,2′:6′,2′′-terpyridine, bpy ) 2,2′-bipyridine; R ) C 6 H 4 F-4 (1), C 6 H 4 Cl-4 (2), C 6 H 5 (3), C 6 H 4 Me-4 (4), C 6 H 4 OMe-4 (5), t-Bu (6), (C 6 H 4 CtC) n C 6 H 5 [n ) 1 (7) and 2 (8)]) and [(tpy)(bpy)RudC(OMe)(CH 2 R)] 2+ (R ) C 6 H 4 OMe-4 (9), t-Bu (10)) have been prepared. The molecular structures of 4(PF 6 ), 5(PF 6 ), and 9(ClO 4 ) 2 reveal Ru-C distances of 2.025(9), 2.025(7), and 1.933(6) Å, respectively. The Ru(III/II) oxidation waves are irreversible for 1-8 (E pa ) 0.15-0.26 V vs FeCp 2 +/0 ) but reversible for 9 and 10 (E 1/2 ) 0.99 and 1.00 V, respectively). The absorption bands in the visible region for 1-8 (λ max ) 502-526 nm) and 9 and 10 (λ max ca. 410 nm) are assigned as d π (Ru II ) f π*(polypyridine) MLCT transitions. Complexes 1-8 weakly emit at λ max ) 748-786 nm in CH 3 CN solution at 298 K (λ ex ) 550 nm). Complexes 9 and 10 are nonemissive in CH 2 Cl 2 solution at 298 K, but in glassy n-butyronitrile at 77 K, excitation at λ ) 415 nm produces emission at λ max ) 597 and 615 nm, respectively. These emissions are tentatively ascribed as d π (Ru II ) f π*(polypyridyl) 3 MLCT in nature. The carbene derivatives 9 and 10 undergo photochemical reactions upon irradiation in solution, and [(tpy)(bpy)RuNtCCH 3 ] 2+ and 4-methoxybenzaldehyde were isolated from the photolysis of 9 in CH 3 CN.

Emissive cyanide-bridged bimetallic compounds as building blocks for polymeric antennae

“…Dalton Transactions (ca. 1 × 10 −3 ) are similar to those reported for the closely related monomers [19][20][21][22][23][24]43,44 and point to the triplet MLCT of the ruthenium polypyridine as the emissive state. The preservation of these photophysical properties indicates that the addition of a second metal ion from the 2nd or 3rd transition series (with a d 6 configuration) does not introduce competitive non-radiative pathways.…”

“…Lifetimes (between 10 and 50 ns) and emission quantum yields (ca. 1x10 -3 ) are similar to those reported for the closely related monomers [19][20][21][22][23][24]43,44 and points to the triplet MLCT of the ruthenium polypiridine as the emissive state. The preservation of these photophysical properties indicates that addition of a second metal-ion from the 2 nd or 3 rd transition series (with a d 6 and S9), these complexes present a low energy MM`CT state which may be responsible for the oxidative quenching of the excited state emission.…”

Tuning the Copper(II)/Copper(I) Redox Potential for More Robust Copper‐Catalyzed C–N Bond Forming Reactions

“…The unbound phen ligand has been known to lower the cathodic region with one electron quasi‐reversible waves . The Cu 2+ /Cu + redox wave for phenanthroline complexes has been shown to occur between 200 and 1200 mV (vs. NHE) depending on the substitution present on the ligand .…”

Ligand‐to‐Ligand Charge‐Transfer Transitions of Platinum(II) Complexes with Arylacetylide Ligands with Different Chain Lengths: Spectroscopic Characterization, Effect of Molecular Conformations, and Density Functional Theory Calculations

“…+ (n = 1-3; bpy = 2,2-bipyridine, Ph = phenyl), [5] [AuA C H T U N G T R E N N U N G (Cy 3 P)-A C H T U N G T R E N N U N G {CCA C H T U N G T R E N N U N G (C 6 H 4 CC) nÀ1 Ph}] + (n = 1-4; PCy 3 = tricyclohexylphosphine), [6] …”