Home About us Contact
|
Home About us Contact | ||
|
|
||
P Orbital (p + orbital)
Selected AbstractsElectronic structures and chemical bonding in diatomic ScX to ZnX (X = S, Se, Te)JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2007Z. J. Wu Abstract Bond distances, vibrational frequencies, electron affinities, ionization potentials, dissociation energies, and dipole moments of the title molecules in neutral, positively, and negatively charged ions were studied using density functional method. Ground electronic state was assigned for each molecule. The bonding patterns were analyzed and compared with both the available data and across the series. It was found that, besides ionic component, covalent bonds are formed between the metal s, d orbitals, and the p orbital of S, Se, and Te. For neutral and cationic molecules, the covalent character increases from ScX to CrX and from FeX to CuX with an exception of decrease at MnX and ZnX, while for anionic molecules, the trend is not obvious. For both neutral and charged molecules, the sulfides have the shortest bond distance and largest vibrational frequency, while tellurides have the largest bond distance and smallest vibrational frequency. For neutral and anionic molecules, the dissociation energy of sulfides is the largest, that of tellurides is the smallest, while this only remains true for cationic molecules from ScX+ to FeX+. © 2006 Wiley Periodicals, Inc. J Comput Chem 28: 703,714, 2007 [source] Excited-state structure by time-resolved X-ray diffractionACTA CRYSTALLOGRAPHICA SECTION A, Issue 2 2002Christopher D. Kim X-ray crystallography has traditionally been limited to the study of the ground-state structure of molecules and solids. Recent technical advances are removing this limitation as demonstrated here by a time-resolved stroboscopic study of the photo-induced 50,µs lifetime excited triplet state of the [Pt2(pop)4]4, ion [pop = pyrophosphate, (H2P2O5)2,], performed at helium temperatures with synchrotron radiation. The shortening of the Pt,Pt bond by 0.28,(9),Å upon excitation is compatible with the proposed mechanism involving promotion of a Pt,Pt antibonding d,* electron to a weakly bonding p orbital. The contraction is accompanied by a 3° molecular rotation. The time-resolved diffraction technique described here is applicable to reversible light-driven processes in the crystalline solid state. [source] Synthesis and nuclear magnetic resonance spectroscopic studies of 1-arylpyrrolesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2000Chang Kiu Lee A series of m - and p -substituted 1-phenyl, 1-benzyl, 1-benzoyl, and 1-(2-phenylethyl)pyrroles was prepared and their 1H and 13C nmr spectroscopic characteristics were examined. In general, good correlations were observed between the chemical shift values of the ,H and the ,C of pyrroles [except 1-(2-phenylethyl)pyrroles] and the Hammettt ,. The observation may be explained in terms of the electronic effects of the substituents which are transmitted through bonds and through space by interaction of the p orbitals between ,Cs of the pyrrole ring and m - and pCs of the phenyl ring. Substituent constants of 1-pyrrolyl, 1-pyrrolylmethyl, and 1-pyrroloyl groups for the 1H and 13C chemical shifts of phenyl ring are also presented. [source] Spectral Properties of Pro-multimodal Imaging Agents Derived from a NIR Dye and a Metal ChelatorPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2005Zongren Zhang ABSTRACT Monomolecular multimodal imaging agents (MOMIAs) are able to provide complementary diagnostic information of a target diseased tissue. We developed a convenient solid-phase approach to construct two pro-MOMIAs (before incorporating radiometal) derived from 1,4,7,10-tetraazacy-clododecane-1,4,7,10-tetraacetic acid (DOTA) and cypate, a near-infrared (NIR) fluorescent dye analogous to indocyanine green (ICG). The possible interaction between d orbitals of transition metal DOTA complexes or free metals and the p orbitals of cypate chromophore could quench the fluorescence of pro-MOMIAs. However, we did not observe significant changes in the spectral properties of cypate upon conjugation with DOTA and subsequent chelation with metals. The fluorescence intensity of the chelated and nonmetal-chelated PRO-MOMIAs remained fairly the same in dilute 20% aqueous dimethylsulfoxide (DMSO) solution (1 × 10,6M). Significant reduction in the fluorescence intensity of pro-MOMIAs occurred in the presence of a large excess of metal ions (> 1 molar ratio for indium and 20-fold for a copper relative to pro-MOMIA). This study suggests the feasibility of using MOMIAs for combined optical and radioisotope imaging. [source] | ||||||||||