Energy transfer pathways in dinuclear heteroleptic polypyridyl complexes: through-space vs through-bond interaction mechanisms

A series of homo- and heteronuclear ruthenium and osmium polypyridyl complexes with the bridging ligands 1,3-bis(5-(2-pyridyl)-1H-1,2,4-triazol-3-yl)benzene (H(2)mL) and 1,4-bis(5-(2-pyridyl)-1H-1,2,4-triazol-3-yl)benzene (H(2)pL) are reported. The photophysical properties of these compounds are investigated, and particular attention is paid to the heteronuclear (RuOs) compounds, which exhibit dual emission. This is in contrast to phenyl-bridged polypyridine Ru-Os complexes with a similar metal-metal distance, in which the Ru emission is strongly quenched because the nature of the bridging ligand allows for an efficient through-bond coupling. The results obtained for the compounds reported here suggest that energy transfer is predominantly taking place via a dipole-dipole, F?rster type, mechanism, that may dominate when through-bond coupling is weak. This is in stark contrast to ground state interaction, which is found to be critically dependent on the nature of the bridging unit employed.     

稀土离子与伴清蛋白结合的光谱研究

在ｐＨ＝７．４和２５℃下，用紫外吸收差光谱进行了Ｅｕ＾３＋对脱伯伴清蛋白的滴定，Ｅｕ＾３＋与脱铁伴清蛋白结合后其差光谱在２４５ｎｍ和２９６ｎｍ处出现吸收峰，在２４５ｎｍ处Ｅｕ＾３＋脱铁伴清旧白配合物的摩尔吸光系数是（２．１±０．１）×１０＾４ｃｍ＾－１．Ｌ．ｍｏｌ＾－１，Ｅｕ＾３＋可占据脱铁伴清蛋白的２个金属离子结合部位，条件平衡常数ｌｏＫＮ＝８．２１±０．２０，ｌｇＫｃ＝４．６０±０．１１，脱铁     

Toward subchemical accuracy in computational thermochemistry: focal point analysis of the heat of formation of NCO and [H,N,C,O] isomers

In continuing pursuit of thermochemical accuracy to the level of 0.1 kcal mol(-1), the heats of formation of NCO, HNCO, HOCN, HCNO, and HONC have been rigorously determined using state-of-the-art ab initio electronic structure theory, including conventional coupled cluster methods [coupled cluster singles and doubles (CCSD), CCSD with perturbative triples (CCSD(T)), and full coupled cluster through triple excitations (CCSDT)] with large basis sets, conjoined in cases with explicitly correlated MP2-R12/A computations. Limits of valence and all-electron correlation energies were extrapolated via focal point analysis using correlation consistent basis sets of the form cc-pVXZ (X=2-6) and cc-pCVXZ (X=2-5), respectively. In order to reach subchemical accuracy targets, core correlation, spin-orbit coupling, special relativity, the diagonal Born-Oppenheimer correction, and anharmonicity in zero-point vibrational energies were accounted for. Various coupled cluster schemes for partially including connected quadruple excitations were also explored, although none of these approaches gave reliable improvements over CCSDT theory. Based on numerous, independent thermochemical paths, each designed to balance residual ab initio errors, our final proposals are DeltaH(f,0) ( composite function )(NCO)=+30.5, DeltaH(f,0) ( composite function )(HNCO)=-27.6, DeltaH(f,0) ( composite function )(HOCN)=-3.1, DeltaH(f,0) ( composite function )(HCNO)=+40.9, and DeltaH(f,0) ( composite function )(HONC)=+56.3 kcal mol(-1). The internal consistency and convergence behavior of the data suggests accuracies of +/-0.2 kcal mol(-1) in these predictions, except perhaps in the HCNO case. However, the possibility of somewhat larger systematic errors cannot be excluded, and the need for CCSDTQ [full coupled cluster through quadruple excitations] computations to eliminate remaining uncertainties is apparent.     

Competitive inhibition ELISA for quantification of Ara h 1 and Ara h 2, the major allergens of peanuts

Allergies to peanuts are becoming an increasingly important health problem as a result of the persistence and severity of the reaction in allergic individuals. Because no treatment currently is available, avoidance is the only option for peanut-allergic individuals. Avoidance of an abundant and often disguised food such as peanuts, however, is very difficult; therefore, competitive inhibition ELISAs were developed to detect and quantitate each of the major peanut allergens, Ara h 1 and Ara h 2. Under optimal conditions for each assay, the sensitivity of the Ara h 1 and Ara h 2 detection assays were 12 and 0.5 ng/mL, respectively. These assays were primarily devised to effectively compare the levels of Ara h 1 and Ara h 2 in a wide variety of peanuts or peanut products but can also be used to identify cross-reactive antigens. The method is simple and rapid, requiring only one allergen-specific antibody and, therefore, could be adapted specifically to detect the presence of these individual allergens in different foods.     

The thermolysis of ammonium 12-molybdophosphate

The thermal decomposition of ammonium l2-molybdophosphate, prepared under various conditions was studied on the thermobalance. For the HNO₃ washed precipitate, a drying temperature of 160° to 415° was recommended; for the NH₄NO₃ washed compound, a drying temperature of 260° to 430° should be employed.     

H-C-SiH3: direct generation and spectroscopic identification of ethylidene's cousin

Ground-state triplet silaethylidene, generated directly by the reaction of 3P carbon atoms with silane under matrix isolation conditions in solid Ar (10-12 K), has been thoroughly characterized by the EPR and IR spectra of both the parent and perdeuterated isotopologs. A theoretical anharmonic vibrational analysis based on a CCSD(T)/cc-pVTZ complete quartic force field gave remarkable agreement with the experimental IR fundamentals, generally within 10 cm-1 and without any empirical scaling of the ab initio frequencies. Silaethylidene exhibits a Cs minimum with a H-C-Si angle near 153 degrees , but the barrier to H-C-Si linearity (C3v symmetry) is only 0.24 kcal mol-1. This minuscule barrier can be surmounted by zero-point vibrations, as evident from the EPR data. The triplet stabilizing effect of the electropositive SiH3 group amounts to about 15 kcal mol-1.