A Pt NMR study on zero-magnetic-field splitting and the phosphorescence properties in the excited triplet states of cyclometalated platinum(ii) complexes.

We report the factors governing zero-magnetic-field splitting (zfs) in the lowest-energy electronically excited triplet (T1) states of cyclometalated platinum(ii) complexes, whose zfs energies between the lowest- (φ1) and highest-energy spin-sublevels (φ3) in the T1 states (ΔEzfs) are already known: [Pt(bhq)(dpm)] (1Pt), [Pt(thpy)(acac)] (2Pt), [Pt(ppy)(acac)] (3Pt), cis-[Pt(thpy)2 (4Pt), and cis-[Pt(ppy)2] (5Pt), where bhq, dpm, thpy, acac, and ppy are benzo[h]quinoline, dipivaloylmethane, 2-(2-thienyl)pyridine, acetylacetone, and 2-phenylpyridine, respectively. As one of the important findings, we show the relationship between the ΔEzfs and 195Pt NMR chemical shifts of the five Pt(ii) complexes. The implications of the ΔEzfs values on the emission properties of the Pt(ii) complexes in acetonitrile at 293 K are also discussed.

Synthesis, Structures, and Photoluminescent Properties of Tricyanidonitridorhenium(V) Complexes with Bipyridine-Type Ligands.

Tricyanidonitridorhenium(V) complexes with 2,2'-bipyridine (bpy) derivatives in which the 4 and 4' positions were substituted by X, [ReN(CN)(Xbpy)] (X = NMe, NH, OMe, Me, Cl, and Br), were newly synthesized and characterized. The structures of the new complexes were determined by single-crystal X-ray analysis. UV-vis spectra of the complexes in dimethyl sulfoxide (DMSO) showed that the peak maximum wavelengths of rhenium-to-π* bpy-type-ligand charge transfer were in the range of 474-542 nm.

Terminal Ligand (L) Effects on Zero-Magnetic-Field Splitting in the Excited Triplet States of [{MoBr}L] (L = Aromatic Carboxylates).

We report the emission properties of the octahedral hexamolybdenum(II) bromide-core ({MoBr}) clusters having a series of terminal aromatic carboxylate ligands (RCOO), [{MoBr}(RCOO)], in solution and crystalline phases. The acid dissociation constant of RCOOH (p K(L)) was shown to govern the redox and emission properties of the clusters. Temperature ( T)-controlled emission experiments (3-300 K) demonstrated that the clusters showed large T-dependent emission energies (ν̃) and lifetimes (τ) because of zero-magnetic-field splitting in the emissive excited triplet (T) states.

Zero-Magnetic-Field Splitting in the Excited Triplet States of Octahedral Hexanuclear Molybdenum(II) Clusters: [{MoX}Y] (X, Y = Cl, Br, I).

The temperature ( T) dependences of the emissions from the tetra- n-butylammonium salts of [{MoX}Y] (X, Y = Cl, Br, and I) in optically transparent polyethylene glycol dimethacrylate matrixes were studied in the T range of 3-300 K. [{MoCl}Y], [{MoBr}Y], and [{MoI}I] showed the T-dependent emission characteristics similar to those of other hexanuclear Mo(II), Re(III), and W(II) clusters reported previously, while [{MoI}Br] and [{MoI}Cl] exhibited the emission properties different from those of other [{MoX}Y] clusters. The photophysical behavior of these clusters was explained by the excited triplet state spin-sublevel ( Φ, n = 1-4) model irrespective of the nature of X and Y.

A study on the redox, spectroscopic, and photophysical characteristics of a series of octahedral hexamolybdenum(ii) clusters: [{MoX}Y] (X, Y = Cl, Br, or I).

We report a systematic study on the redox, spectroscopic, and photophysical properties of a series of [{MoX}Y] (X, Y = Cl, Br, or I. 1-9). All of the [{MoX}Y] clusters show intense and long-lived phosphorescence in both CHCN and crystalline phases at 298 K.

Zero-Magnetic-Field Splitting in the Excited Triplet States of Octahedral Hexanuclear Molybdenum(II) Clusters: [{MoX}(n-CFCOO)] (X = Cl, Br, or I).

Temperature (T)-dependent emission from [{MoX}(n-CFCOO)] (X = Cl (1), Br (2), and I (3)) in optically transparent polyethylene glycol dimethacrylate matrices were studied in 3 K < T < 300 K to elucidate the spectroscopic and photophysical properties of the clusters, in special reference to zero-magnetic-field splitting (zfs) in the lowest-energy excited triplet states (T) of the clusters. The cluster complexes 1 and 2 showed the T-dependent emission characteristics similar to those of [{MoCl}Cl], while 3 exhibited emission properties different completely from those of 1 and 2. Such T-dependent emission characteristics of 1, 2, and 3 were explained successfully by the excited triplet state spin-sublevel (Φ, n = 1-4) model.

Quasi-One-Step Six-Electron Electrochemical Reduction of an Octahedral Hexanuclear Molybdenum(II) Cluster.

We report for the first time quasi-one-step six-electron electrochemical reduction of a new hexanuclear molybdenum(II) bromide cluster having terminal 3,5-dinitrobenzoate ligands: [MoBr(DNBA)]. The electrochemical responses of the cluster were studied based on cyclic (CV), differential pulse, and normal pulse voltammetries, together with the analytical simulations of the CV and spectroelectrochemistry. CV simulations have revealed that the electrochemical reaction of the cluster proceeds in an EEEEEE scheme, and the potential differences between the two adjacent reduction steps are in the range of 15-30 mV.

Synthetic Tuning of Redox, Spectroscopic, and Photophysical Properties of {Mo6I8}(4+) Core Cluster Complexes by Terminal Carboxylate Ligands.

The reactions between the tetra-n-butylammonium salt of [{Mo6I8}I6](2-) and silver carboxylates RCOOAg (R = CH3 (1), C(CH3)3 (2), α-C4H3O (3), C6H5 (4), α-C10H7 (5), or C2F5 (6)) in CH2Cl2 afforded new carboxylate complexes [{Mo6I8}(RCOO)6](2-). The complexes were characterized by X-ray single-crystal diffraction and elemental analysis, cyclic/differential pulse voltammetry, and IR, NMR, and UV-visible spectroscopies. The emission properties of the complexes 1-6, and those of the earlier reported complexes with R = CF3 (7) and n-C3F7 (8), were studied both in acetonitrile solution and in the solid state.