Room-temperature phosphorescence of anilinonaphthalenesulfonate “fluorescence probe” compounds

2,6-anilinonaphthalenesulfonate (2,6-ANS) and 2,6-toluidinonaphthalenesulfonate (2,6-TNS) exhibit room-temperature phosphorescence when absorbed on filter paper, but the corresponding 1,8-isomers (1,8-ANS and 1,8-TNS) do not. The phosphorescence of the 2,6-isomers and nonphosphorescence of the 1,8-isomers is also found to hold in rigid glass at 77 K. No phosphorescence was detectable from N-phenyl-1-napthylamine at room temperature or 77 K, indicating that intramolecular hydrogen bonding in the 1,8-isomers isomers is not an essential feature inhibiting phosphorescence. Very effective heavy-atom enhancement of the phosphorescences of 2,6-ANS and 2,6-TNS by sodium iodide is observed.     

Analytical results for the electronic shell structure in mesoscopic systems: Balian-Bloch type theory for spheres,discs, rings and anti-dot lattices

The electronic shell structure resulting from the interference of closed orbital paths is determined for mesoscopic systems like spherical clusters, discs and rings by extending the semiclassical theory of Balian and Bloch. Analytical results for the shell structure in the density of states are obtained. Thus, the dependence of the shell structure on dimension, size and geometry and potential of the mesoscopic system and on an external magnetic field can be studied systematically. Comparison of the semiclassical results and those of quantum mechanical calculations permits analysis of typical quantum mechanical effects and shows the validity of the semiclassical theory. Our results should stimulate new experiments, can be used to calculate oscillations in the binding-energy, ionization-potential, and can be applied to analyze oscillations in the electronic density of states of quantum dot systems like anti-dot lattices.     

Kinetics of the phosphorescent triplet states of tetracyanobenzene complexes as studied by microwave induced delayed phosphorescence

Using microwave induced delayed phosphorescence techniques we determined the populating and depopulating rate constants for the individual spin-sublevels of the phosphorescent states of tetracyanobenzene (TCNB) and its charge-transfer complexes with benzene and hexamethylbenzene (HMB) in n-hexane at 1.25 K. It was shown that the non-radiative decay process from the shortest lifetime sublevel is most responsible for the previously observed shortening in the phosphorescence lifetime of the TCNBHMB complex.     

Spectroscopic study of the dispiro-1,2,4,5-tetroxane (cyclohexanone diperoxide)

The aim of this work is to present results derived from experimental IR and UV spectra and theoretical studies of DPCH, in order to get a more deeper insight on the physicochemical properties of this compound to gain a more deep knowledge of its action, helping in the design of new compounds with antimalaric effects. Experimental results are analyzed on the basis of theoretical calculations, which allow to derive suitable interpretations of spectral data.     

Microwave spectrum, molecular structure, and theoretical calculation of cyclohexanone oxime (chair form)

The microwave spectra of cyclohexanone oxime and d₁ (=NOD) and d₄(2,2,6,6-d₄) derivatives were observed in the frequency range from 8 to 40 GHz in the ground and excited vibrational states. The rotational constants were determined to be A = 3799.844(48), B = 1513.7912(23), and C = 1189.6118(29) MHz for normal species, A = 3791.835(88), B = 1461.0324(47), and C = 1157.5653(53) MHz for d₁ species, and A = 3364.141(49), B = 1487.9551(34), and C = 1154.0965(44) MHz for d₄ species in the ground vibrational state. The planar moments, P_bb (P_bb = (I_c + I_a − I_b)/2) of normal, d₁, and d₄ species were determined to be 111.9885(26), 111.9817(46), and 124.2394(49) uŲ, respectively. The almost same values of P_bb of normal and d₁ species suggest that the hydroxyl hydrogen atom is very close to the a-c plane. From the r_s coordinates of the hydroxyl hydrogen atom, the OH bond was found to be at the trans position with respect to the CN double bond. The conformation of cyclohexanone oxime was determined to be chair form by comparing the observed and calculated rotational constants, ΔI, and planar moments, and taking account of the calculated the relative energy difference, ΔE. The structural parameters, the three bond lengths, three bond angles, and three dihedral angles, were adjusted to the nine rotational constants observed. The bond angle of ∠C₂C₁N is much wider than that of ∠C₆C₁N by about 10°. The dihedral angles of ∠C₁C₂C₃C₄, ∠C₂C₃C₄C₅, and ∠C₃C₄C₅C₆ were determined to be 53.3(5), −57.2(5), and 57.2(5)°. Two vibrational modes were assigned to the ring-bending and ring-twisting ones, which are almost harmonic up to v = 3.     

A tailor designed fluorescent ‘turn-on’ sensor of formaldehyde based on the BODIPY motif

Based on theoretical calculations on the effects of molecular orbital energy levels of amines on the fluorescence properties of the fluorophore, aniline-substituted BODIPY motif (AnB) with quenched fluorescence was developed as a ‘turn-on’ switch for the qualitative and quantitative detection of formaldehyde with the detection limit (LOD) of ca. 165 nM.     

Synthesis,characterization, and crystal structure of a Ni(II) complex of an acyclic pentadentate Schiff base; an agreement between the experimental and theoretical results

A Ni(II) complex of an acyclic pentadentate Schiff base was prepared by template condensation of two equivalents of 2-acetylpyridine with one equivalent of bis(3-aminopropyl)amine in the presence of Ni(II) in methanol. The resulting complex, [NiL₃₃(MeOH)](ClO₄)₂ · CH₃OH, was characterized by X-ray crystallography, elemental analysis, and IR spectrophotometry. The X-ray crystallographic structure revealed a six-coordinate, distorted octahedral geometry in which the sixth coordination being achieved by a methanol molecule. A theoretical study at DFT (B3LYP) level using standard 6-31G* basis set for ligand atoms and LanL2DZ for metal showed that the experimentally determined structure of the cation is about 8–20 kcal mol^?1 more stable than its geometrical isomers.