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

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

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

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

Light-Driven Reduction of CO₂ to CO in Water with a Cobalt Molecular Catalyst and an Organic Sensitizer

We report an efficient visible light-driven CO2 reduction system that functions in water and without any noble metal nor rare materials. Using the cobalt complex [Co(qpy)(OH2)2]2+ (1, qpy = 2,2′:6′,2″:6″,2‴-quaterpyridine) as a catalyst, an organic triazatriangulenium (TATA+) salt as the photosensitizer (PS), BIH + TEOA (BIH = 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole and TEOA = triethanolamine) as the sacrificial reductant (SD), CO and formate were first produced with a total TON >3700 upon irradiation in CO2-saturated CH3CN solution with visible light. Upon the addition of a weak Brönsted acid (water), catalysis was enhanced and directed toward CO production (19,000 TON, 93% selectivity). The photocatalytic system was further shown to function in pure water as a solvent. High metrics with a TON for CO of 2600 and 94% selectivity were obtained using TEA (triethylamine) as the SD

Slow Magnetic Relaxation in a Series of Mononuclear 8‑Coordinate Fe(II) and Co(II) Complexes

A series of homoleptic mononuclear 8-coordinate Fe^II and Co^II compounds, [Fe^II(<b>L</b>^<b>2</b>)₂]­(ClO₄)₂ (<b>2</b>), [Fe^II(<b>L</b>^<b>3</b>)₂]­(ClO₄)₂ (<b>3</b>), [Fe^II(<b>L</b>^<b>4</b>)₂]­(ClO₄)₂ (<b>4</b>), [Co^II(<b>L</b>^<b>1</b>)₂]­(ClO₄)₂ (<b>5</b>), [Co^II(<b>L</b>^<b>2</b>)₂]­(ClO₄)₂ (<b>6</b>), [Co^II(<b>L</b>^<b>3</b>)₂]­(ClO₄)₂ (<b>7</b>), and [Co^II(<b>L</b>^<b>4</b>)₂]­(ClO₄)₂ (<b>8</b>) (<b>L</b>^<b>1</b> and <b>L</b>^<b>2</b> are 2,9-dialkylcarboxylate-1,10-phenanthroline ligands; <b>L</b>^<b>3</b> and <b>L</b>^<b>4</b> are 6,6′-dialkylcarboxylate-2,2′-bipyridine ligands), have been obtained, and their crystal structures have been determined by X-ray crystallography. The metal center in all of these compounds has an oversaturated coordination number of 8, which is completed by two neutral homoleptic tetradentate ligands and is unconventional in 3d-metal compounds. These compounds are further characterized by electronic spectroscopy, cyclic voltammetry (CV), and magnetic measurements. CV measurements of these complexes in MeCN solution exhibit rich redox properties. Magnetic measurements on these compounds demonstrate that the observed single-ion magnetic (SIM) behavior in the previously reported [Fe^II(<b>L</b><b>¹</b>)₂]­(ClO₄)₂ (<b>1</b>) is not a contingent case, since all of the 8-coordinate compounds <b>2</b>–<b>8</b> exhibit interesting slow magnetic relaxation under applied direct current fields