Do Anionic π Molecules Aggregate in Solution? A Case Study with Multi-interactive Ligands and Network Formation

An anionic π molecule can form an aggregate when a multi-interactivity is introduced, in sharp contrast to common anionic molecules that are generally difficult to stack on each other. We found that a multi-interactive ligand, 2,5,8-tri(4′-pyridyl)-1,3,4,6,7,9-hexaazaphenalenate (TPHAP⁻) exhibited a large Stokes shift and an intramolecular charge transfer, both of which were sensitive to hydrogen-bonding media. An anionic potassium salt of TPHAP⁻ in methanol formed various aggregation states depending on the concentration examined; this was revealed by steady-state spectroscopic and fluorescence lifetime measurements. Self-assembling cadmium ions and the ligands can create several morphological crystals that are controlled by the ligand concentration, among which three new structures were determined by single-crystal analysis. The X-ray structures obtained suggest that the aggregation states of the ligand in solution can be transferred to the solid system of the porous coordination networks.     

Ultra-High Quality Cavity with 1.5 ppm Loss at 1064 nm

Characterization of an ultra-low loss and high finesse Fabry-Perot cavity at 1064 nm is reported. The characteristics are obtained from measurements of cavity decay time, frequency response and transmission efficiency. The results show that the mirrors have the loss of 1.5 ppm including absorption and scattering losses and the reflectance of 99.9873% which corresponds to a cavity finesse of 2.48X10⁴.     

Organic solid photochromism by photoreduction mechanism: Polar aprotic viologen copolymers

Copolymers of vinyl viologens such as N-vinylbenzyl-N′-yalkyl and N-(γ-methyacryloyloxy)propyl-N′-propyl-4,4′-bipyridinium dihalides and polar aprotic comonomers such as N-vinyl-2-pyrrolidone (VP) and N,N-dimethylacrylamide (DMA) were prepared by the copolymerizations of vinyl viologens with DMA and the chemical modifications of VP copolymers containing reactive halogens. Copolymers containing various viologen anions such as Br^?, BF, SO, and I^? were also prepared by the anion exchange of copolymers containing Cl^?. The photocolor developments of these aprotic copolymers in the film state were completely reversible and faster than for the corresponding copolymers with protic comonomers such as acrylamide and 2-hydroxyethyl acrylate, all with characteristic absorption spectra attributable to single radical cations.     

SOLVENT EFFECT ON SPHEROIDENE IN NONPOLAR AND POLAR SOLUTIONS AND THE ENVIRONMENT OF SPHEROIDENE IN THE LIGHT-HARVESTING COMPLEXES OF Rhodobacter sphaeroides 2.4.1 AS REVEALED BY THE ENERGY OF THE 1Ag−→1Bu+ ABSORPTION AND THE FREQUENCIES OF THE VIBRONICALLY COUPLED C=C STRETCHING RAMAN LINES IN THE 1Ag− AND 1Bu− STATES

Abstract –The ¹A_g^?→¹B_u⁺ electronic absorption band and the vibronically coupled, C=C stretching Raman lines in the ¹A_g^? and 2¹A_g^? states were recorded for spheroidene free in nonpolar and polar solvents as well as for spheroidene bound to the LH1 and LH2 complexes of Rhodobacter sphaeroides 2.4.1. The ¹B_u⁺ energy exhibited a linear dependence on R(n) = (n² - 1)/(n²+ 2) in both nonpolar and polar solvents; the line for polar solvents had a gentler slope and crossed the line for nonpolar solvents at R(n) = 0.3. The above characteristic of polar solvents was ascribed to the electric field generated by fluctuation of the solvent permanent dipoles; it stabilizes the ¹B_u⁺ energy and reduces the polarizability of the solvent. The vibronically coupled, C=C stretching frequencies in the ¹A_g^? and 2¹A_g^? states [ν(A_g) and [ν(2A_g)] also showed similar dependence on R(n), which is explained in terms of vibronic coupling among the ¹A_g^?, 2¹A_g^? and 3¹A_g^? states. The environment of spheroidene in the LH2 and LH1 complexes was assessed on the basis of the ¹B_u⁺ energy and the ν(A_g) and [ν(2A_g) frequencies: Spheroidene in the LH2 complex is located in an environment with high polarizability, while spheroidene in the LH1 complex is located in an environment with lower polarizability.     

An easy access to 7-methyl-2-naphthalenecarbonitrile

A practical and cost-effective procedure has been developed for the synthesis of 7-methyl-2-naphthalenecarbonitrile, the precursor of the anticoagulant agents YM-60828 or YM-96765. This new route generates the key intermediate in only two steps from readily available 3-cyanopropionaldehyde dimethyl acetal and m-tolualdehyde, without requiring chromatographic purification. The synthesis involves condensation of the cyano derivative with the aldehyde and subsequent cyclodehydration.