A new series of substituted hydrazone complexes, [Cu(Hpbph)I] (1), [Cu(Hpbph)PPh3]PF6 (2-PF6), [NiCl(Hpbph)]Cl (3-Cl), [PtCl(Hpbph)]ClO4 (4-ClO4), and [PtCl(pbph)] (4b) (Hpbph = 2-(diphenylphosphino)benzaldehyde 2-pyridylhydrazone) have been synthesized and characterized. X-ray crystallography revealed that the copper(I) complexes adopt pseudo-tetrahedral geometry, while the nickel(II) and platinum(II) complexes provide square-planar forms. All the complexes exhibit distinct color changes on the basis of the deprotonation/protonation on the ligand although their acid/base behaviors are largely different. The acidity constants (pKa) in methanol were determined to be 11.4 (1), 12.5 (2), 7.7 (3), and 6.7 (4). The results indicate that the dissociation of the proton on the ligand strongly depends on the ligand deformation controlled by the coordination geometry of the complexes and ancillary ligands also somewhat affect the acidity.

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Photoreactivities of Ni(II)- and Pt(II)-hydrazone complexes, [NiCl(L)] (Ni1) and [PtCl(L)] (Pt1), respectively [HL = 2-(diphenylphosphino)benzaldehyde-2-pyridylhydrazone], were investigated in detail via UV-vis absorption, (1)H nuclear magnetic resonance (NMR) spectroscopy, and electrospray ionization time-of-flight (ESI-TOF) mass spectrometry; the two photoproducts obtained from the photoreaction of Pt1 were also successfully identified via X-ray analysis. The absorption bands of the Ni1 and Pt1 complexes were very similar, centered around 530 nm, and were assigned as an intraligand charge transfer transition of the hydrazone moiety. The absorption spectrum of Pt1 in a CH3CN solution changed drastically upon photoirradiation (λ = 530 nm), whereas no change was observed for Ni1. (1)H NMR and ESI-TOF mass spectra under various conditions suggested that the photoexcited Pt1* reacts with dissolved dioxygen to form a reactive intermediate, and the ensuing dark reactions afforded two different products without any decomposition. In contrast to the simple photo-oxidation of HL to form a phosphine oxide HL(P═O), the X-ray crystallographic analyses of the photoproducts clearly indicate the formation of a mononuclear Pt complex with the oxygenated hydrazone ligand (Pt1O) and a dinuclear Pt complex with the oxygenated and dimerized hydrazone ligand (Pt2). The photosensitized reaction in the presence of an (1)O2-generating photosensitizer, methylene blue (MB), also produced Pt1O and Pt2, indicating that the reaction between (1)O2 and ground-state Pt1 is the important step. In a highly viscous dimethyl sulfoxide solution, Pt1 was slowly, but quantitatively, converted to the mononuclear form, Pt1O, without the formation of the dinuclear product, Pt2, upon photoirradiation (and in the reaction photosensitized by MB), suggesting that this photoreaction of Pt1 involves at least one diffusion-controlled reaction. On the other hand, the same complexes Pt1O and Pt2 were also produced in the degassed solution, probably because of the reaction of the photoexcited Pt1* with the biradical character and H2O.

2,5-Anhydro-D-mannitol with a fixed furanose ring stimulated the sugar receptor of the flesh fly and reacted with the furanose site. This is the first direct evidence that a furanose can stimulate the sugar receptor and supports strongly the assumption that beta-D-fructofuranose is the only stimulatory component in the solution of D-fructose. Rigid stereospecificity of the furanose site in the sugar receptor is discussed according to the effectiveness of various synthetic 2,5-anhydro-D-hexitols and related compounds. At least four receptor sites are concluded to be in a single sugar receptor: a pyranose (P) site, a furanose (F) site, an aliphatic carboxylate (R) site and an aromatic amino acid (Ar) site.