3 research outputs found
Matrix Effects on Photoluminescence and Oxygen Sensitivity of a Molecular Ruby
The molecular ruby analogue [Cr(ddpd)2]3+ (ddpd=N,NââdimethylâN,Nââdipyridineâ2âylpyridineâ2,6âdiamine) exhibits near infrared (NIR) emission with a high photoluminescence (PL) quantum yield ΊPL of 11â% and a lifetime of 898â
ÎŒs in deaerated water at room temperature. While ligandâbased control of the photophysical properties has received much attention, influences of the counter anions and microenvironment are still underexplored. In this study, the luminescence properties of the molecular ruby were systematically examined for the counter anions Clâ, Brâ, [BF4]â, [PF6]â, [BPh4]â, and [BArF24]â in acetonitrile (MeCN) solution, in crystals, and embedded into polystyrene nanoparticles (PSNP). SternâVolmer analyses of the oxygen quenching studies in the intensity and lifetime domain showed the highest oxygen sensitivity of the complexes with the counter anions of [BF4]â and [BArF24]â, which also revealed the longest luminescence lifetimes. Embedding [Cr(ddpd)2][PF6]3 in PSNPs and shielding with poly(vinyl alcohol) yields a strongly NIRâemissive oxygenâinsensitive material with a record ΊPL of 15.2â% under ambient conditions
Strong circularly polarized luminescence of an octahedral chromium(iii) complex
The chiral spinâflip luminophore [Cr(ddpd)2]3+ can be resolved into enantiopure material by chiral HPLC. The corresponding enantiomers show very high luminescence dissymmetry factors of up to âŁglum âŁâ 0.093 in circularly polarized luminescence (CPL) measurements for the âruby-likeâ phosphorescence transition 2E/2T1 â 4A2 in the near-IR region around λ â 775 nm
A simple yet stable molybdenum(0) carbonyl complex for upconver-sion and photoredox catalysis
Photoactive complexes with earth-abundant metals have attracted increasing interest in the recent years fueled by the promise of sustainable photochemistry. However, sophisticated ligands with complicated syntheses are oftentimes required to enable photoactivity with non-precious metals. Here, we combine a cheap metal with simple ligands to easily access a photoactive complex. Specifically, we synthesize the molybdenum(0) carbonyl complex Mo(CO)3(tpe) featuring the tripodal ligand tris(pyridyl)ethane (tpe) in two steps with high overall yield. The complex shows intense deep-red phosphorescence with excited state lifetimes of several hundred nanoseconds. Time-resolved infrared spectroscopy and laser flash photolysis reveal a triplet metal-to-ligand charge-transfer (3MLCT) state as lowest excited state. Temperature-dependent luminescence complemented by density functional theory (DFT) calculations suggest thermal deactivation of the 3MLCT state via higher lying metal-centered states in analogy to the well-known photophysics of [Ru(bpy)3]2+. Importantly, we found that the title compound is very photostable due to the lack of labilized MoâCO bonds (as caused by trans-coordinated CO) in the facial configuration of the ligands. Finally, we show the versatility of the molybdenum(0) complex in two applications: (1) green-to-blue photon upconversion via a triplet-triplet annihilation mechanism and (2) photoredox catalysis for a green-light driv-en dehalogenation reaction. Overall, our results establish tripodal carbonyl complexes as a promising design strategy to ac-cess stable photoactive complexes of non-precious metals avoiding tedious multi-step syntheses