Michihiro Nishikawa

Intense blue emission and a reversible hypsochromic shift of luminescence caused by grinding based on silver(I) complexes

Silver(I) complexes bearing N-heterocyclic carbene and diphenylphosphinobenzene ligands, [Ag(IPr)(dppbz)]BPh4 (1, IPr = bis(2,6-diisopropylphenyl)imidazole-2-ylidene, dppbz = 1,2-bis(diphenylphosphino)benzene), [Ag(IPr)(dfpbz)]BPh4 (2, dfpbz = 1,2-bis[di(4-fluorophenyl)phosphino]benzene), and [Ag(IPr)(dtbpbz)]BPh4 (3, dtbpbz = 1,2-bis[bis[3,5-di(tert-butyl)phenyl]phosphino]benzene), were newly synthesized and characterized. These complexes, especially 3, exhibit intense blue emission in the solid state. The maximum wavelength and lifetime of the photoluminescence of 3 are 440 nm and 14 μs, respectively. The quantum yield of the photoluminescence of 3 in the solid state is 0.5, which is one of the highest values among blue-emissive silver(I) complexes ever reported. Introduction of bulky tert-butyl groups at 3- and 5-positions of the phenyl groups in the diphosphine ligand plays a key role in both the blue-shift and the enhancement of the photoluminescence. Additionally, the reversible hypsochromic shift of the long-lived emission caused by the grinding process is observed for one of the complexes.

Blue and orange oxygen responsive emissions in the solid state based on copper(I) complexes bearing dodecafluorinated diphosphine and 1,10-phenanthroline derivative ligands

Reversible oxygen sensing abilities based on blue and orange photoluminescence in the solid state are achieved by using newly synthesized copper(I) complexes bearing diimine and dodecafluorinated diphosphine ligands. We found that the blue emission of [Cu(dmp)(dfppe)]PF6 (dmp = 2,9-dimethyl-1,10-phenanthroline, dfppe = 1,2-bis[bis(pentafluorophenyl)phosphino]ethane) in the solid state is very strong under argon, while it is nearly invisible under air. Single crystal X-ray structural analysis reveals that the complex has significant columnar void spaces. [Cu(dmp)(dfppe)]PF6 shows an extremely long lifetime of the emission in the solid state under an argon atmosphere (τ1 = 160 μs (88%), τ2 = 22 μs (12%)), which is one of the largest values for all copper(I) complexes bearing diimine ligands, and it is drastically decreased under air (τ1 = 2.4 μs (85%), τ2 = 0.5 μs (15%)). The employment of the dfppe ligand markedly increases the contribution of ligand centred transition, leading to the long-lived excited state. The orange oxygen responsive emission of [Cu(47dmp)(dfppe)]PF6 (47dmp = 4,7-dimethyl-1,10-phenanthroline) is also examined with the help of an investigation of the photophysics of five new compounds of the copper(I) complexes.

Crystal structure of [N,N-bis­(di­phenyl­phospho­ro­thio­yl)amidato-κ2S,S′]bis­(tri­phenyl­phosphane-κP)copper(I) di­chloro­methane monosolvate

The title compound, [Cu(dppaS2)(PPh3)2], is a neutral mononuclear copper(I) complex bearing an N,N-bis(diphenylphosphorothioyl)amidate (dppaS2 −) ligand and two triphenylphosphane ligands. The structure of this complex was obtained by X-ray diffraction and supported by DFT calculations.

Crystal structure of bis­[μ-1,4-bis­(di­phenyl­phos­phan­yl)butane-κ2P:P′]bis­[(3,4,7,8-tetra­methyl-1,10-phenanthroline-κ2N,N′)copper(I)] bis­(hexa­fluorido­phosphate) di­chloro­methane disolvate

The crystal structure of a dinuclear copper(I) complex bearing bridging 1,4-bis(diphenylphosphanyl)butane and 3,4,7,8-tetramethyl-1,10-phenanthroline ligands is described.

Details of Molecular Bistability Based on Pyrimidine Ring Rotation in Copper(I) Complexes

The rational molecular design requires a detailed investigation for the equilibrium between two rotational isomers derived from orientation of pyrimidine ring. I studied on chemistry of rotational equilibrium in newly synthesized copper(I) complexes bearing two bidentate ligands, pyridylpyrimidine and bulky diphosphine, using 1H NMR and single crystal X-ray structural analysis. I found that ion-pairing sensitivities of rotational bistability in the view point of both thermodynamics and kinetics, evidence for intramolecular process of interconversion, and suitability of common organic solution state for the desired function.

Repeatable Copper(II)/(I) Redox Potential Switching Driven Visible Light-Induced Coordinated Ring Rotation

Repeatable PET-driven rotational isomerization is described. I demonstrated the conversion of light stimuli into electrochemical potential via reversibly working artificial molecular rotation, using two strategies, DMFc+ system and partial oxidation system. In both systems, photoinduced electron transfer from copper complex to electron acceptor plays a key role for the photo- and heat-driven rotation.

Dual Emission Caused by Ring Rotational Isomerization of a Copper(I) Complex

Photophysics of metal complexes is valid for photofunctional devices. Transient emission spectra measurement is a powerful way to find difference in photoprocesses between two rotational isomers which interconvert and coexist in the solution. I developed a molecular system which exhibited heat-sensitive dual luminescence behavior caused by the pyrimidine ring rotational isomerization in copper(I) complexes. This finding is valuable for the novel way to handle the photoprocesses of transition metal complexes.

[μ-Butane-1,4-diylbis(di­phenyl­phos­phane)-κ2P:P′]bis­{[butane-1,4-diylbis(di­phenyl­phosphane)-κ2P,P′]copper(I)} bis­(hexa­fluorido­phosphate) diethyl ether disolvate

In the centrosymmetric dinuclear copper(I) complex cation of the title compound, [Cu2(C28H28P2)3](PF6)2·2C4H10O, the CuI atom is bonded to three P atoms of two butane-1,4-diylbis(diphenylphosphane) (dppb) ligands with a triangular coordination geometry. One of these P atoms belongs to a bridging dppb ligand [Cu—P = 2.2381 (5) Å] and two belong to a chelating dppb ligand [Cu—P = 2.2450 (6) and 2.2628 (5) Å]. The bridging dppb ligand lies on an inversion centre. In the crystal, the cation and the PF6 − anion are linked by C—H⋯F interactions, forming a tape along [110]. The cation and the diethyl ether solvent molecule are also linked by a C—H⋯O interaction.