Unique Hydration/Dehydration-Induced Vapochromic Behavior of a Charge-Transfer Salt Comprising Viologen and Hexacyanidoferrate(II).

We successfully prepared and crystallographically characterized the first intermolecular charge-transfer (CT)-based vapochromic compound, (EV)(HO)[Fe(CN)] (1-Wet, EV: 1,1'-diethyl-4,4'-bipyridine-1,1'-diium), an ethyl viologen-containing CT salt. 1-Wet, which is purple in color, is transformed into a brown powder (1-Dry) upon exposure to methanol vapor, drying over silica gel, or heating; 1-Dry returns to 1-Wet upon exposure to water vapor. These color changes are induced by hydration and dehydration, and gravimetric analyses suggest that 1-Dry is the dehydrated form of 1-Wet, namely, (EV)(H)[Fe(CN)].

Contribution of Coulomb Interactions to a Two-Step Crystal Structure Phase Transformation Coupled with a Significant Change in Spin Crossover Behavior for a Series of Charged Fe Complexes from 2,6-Bis(2-methylthiazol-4-yl)pyridine.

A series of [Fe(L)](BF) compounds were structurally and physically characterized (L = 2,6-bis(2-methylthiazol-4-yl)pyridine). A crystal structure phase transformation from dihydrate compound 1 to anhydrous compound 3 through partially hydrated compounds 2 and 2' upon dehydration was found. Compounds 1 and 3 exhibited a gradual spin crossover (SCO) conversion, whereas compounds 2 and 2' demonstrated two-step and one-step abrupt SCO transitions, respectively.

Design and synthesis of indomethacin analogues that inhibit P-glycoprotein and/or multidrug resistant protein without COX inhibitory activity.

We designed and synthesized conformationally restricted analogues and regioisomers of the nonsteroidal anti-inflammatory drug indomethacin. Evaluation of the inhibitory effects of these compounds on COX, P-glycoprotein, and multidrug resistance indicated that NSAIDS modulation of multidrug-resistant P-glycoprotein and multidrug-resistant protein-1 is not associated with COX-1 and COX-2 inhibitory activities.

Boronic acid-protected gold clusters capable of asymmetric induction: spectral deconvolution analysis of their electronic absorption and magnetic circular dichroism.

Gold clusters protected by 3-mercaptophenylboronic acid (3-MPB) with a mean core diameter of 1.1 nm are successfully isolated, and their absorption, magnetic circular dichroism (MCD), and chiroptical responses in metal-based electronic transition regions, which can be induced by surface D-/L-fructose complexation, are examined. It is well-known that MCD basically corresponds to electronic transitions in the absorption spectrum, so simultaneous deconvolution analysis of electronic absorption and MCD spectra of the gold cluster compound is conducted under the constrained requirement that a single set of Gaussian components be used for their fitting.

Chemical transformation of chiral monolayer-protected gold clusters: observation of ligand size effects on optical and chiroptical responses.

Versatile functionalization of metal clusters is a key step in understanding the reactivity of protective monolayers. We here demonstrate that reaction of the outermost amino groups on (S)-/(R)-penicillamine-protected gold clusters with ethyl isocyanate readily modifies the chiral surface structure through carbamoylation. Interestingly, the clusters are electrophoretically separated by the size of the surface ligand, not by the size of the gold core, which is revealed by UV-vis, IR, and energy dispersive X-ray (EDX) spectroscopy as well as SAXS measurements.

Large optical activity of gold nanocluster enantiomers induced by a pair of optically active penicillamines.

We have succeeded for the first time in preparing a pair of gold nanocluster enantiomers protected by optically active thiols: D- and L-penicillamine (D-Pen and L-Pen). Circular dichroism (CD) spectroscopy confirmed the mirror image relationship between the D-Pen-capped and the L-Pen-capped gold nanoclusters, suggesting that the surface modifier acts as a chiral selector, and that the nanoclusters have well-defined stereostructures as common chiral molecules do. No CD signals could be obtained when the gold nanoclusters were synthesized by using a racemic mixture (rac-Pen).