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排序方式: 共有272条查询结果,搜索用时 59 毫秒
1.
Dr. Amey Nimkar Dr. Sandeepan Maity Prof. Robert A Flowers II Prof. Shmaryahu Hoz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(44):10499-10504
The work described herein compares the effect of additives (HMPA, methanol, ethylene glycol, pinacol, N-methylethanolamine) on thermal and photochemical reactions of samarium diiodide (SmI2). In thermal reactions, additives that coordinate to SmI2 induce a significant increase in reaction rate. In photochemical reactions, the presence of an electronegative atom with a highly localized negative charge on the substrate leads to a rate deceleration. In order to benefit from the columbic interaction with the positively charged samarium cation, these substrates react preferentially by an inner sphere reduction mechanism. The addition of ligands prevents this close interaction causing rate retardation. Furthermore, studies demonstrate that excited state quenching of SmII by ethylene glycol and other additives indicate that it is unlikely to be the major cause for the observed rate retardation. This effect provides a simple diagnostic tool to distinguish between an inner and an outer sphere reduction mechanism. 相似文献
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Acid/Base‐Triggered Switching of Circularly Polarized Luminescence and Electronic Circular Dichroism in Organic and Organometallic Helicenes 下载免费PDF全文
Nidal Saleh Barry Moore II Monika Srebro Nicolas Vanthuyne Loïc Toupet J. A. Gareth Williams Christian Roussel Kirandeep K. Deol Gilles Muller Jochen Autschbach Jeanne Crassous 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(4):1673-1681
Electronic circular dichroism and circularly polarized luminescence acid/base switching activity has been demonstrated in helicene‐bipyridine proligand 1 a and in its “rollover” cycloplatinated derivative 2 a . Whereas proligand 1 a displays a strong bathochromic shift (>160 nm) of the nonpolarized and circularly polarized luminescence upon protonation, complex 2 a displays slightly stronger emission. This strikingly different behavior between singlet emission in the organic helicene and triplet emission in the organometallic derivative has been rationalized by using quantum‐chemical calculations. The very large bathochromic shift of the emission observed upon protonation of azahelicene‐bipyridine 1 a has been attributed to the decrease in aromaticity (promoting a charge‐transfer‐type transition rather than a π–π* transition) as well as an increase in the HOMO–LUMO character of the transition and stabilization of the LUMO level upon protonation. 相似文献
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M. J. R. Cantow T. Y. Ting E. M. Barrall II R. S. Porter E. R. George 《Rheologica Acta》1986,25(1):69-71
The shear dependence of the bulk viscosities of two structurally different types of perfluoropolyether fluids was determined by two different techniques. The first involved direct measurement in a high shear Couette viscometer, the second utilized the time-temperature superposition principle to establish master curves from viscosity determinations at low shear rates and temperature; the results are comparable. Both fluids begin to show non-Newtonian behavior at shear rates above 10,000 s–1. 相似文献
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Timothy P. Moneypenny II Huiying Liu Anna Yang Ian D. Robertson Jeffrey S. Moore 《Journal of polymer science. Part A, Polymer chemistry》2017,55(18):2935-2948
Alkene metathesis has proven to be a powerful method for carbon carbon bond formation, particularly in the field of polymer and materials science. The availability of various tailor-made catalysts not only enables the synthesis of well-defined polymers but facilitates the development of functional, stimuli–responsive materials. This highlight, dedicated to Professor Robert Grubbs on his 75th birthday, focuses on the various research efforts in our group utilizing both alkene and alkyne metatheses and the interesting materials derived from them. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2935–2948 相似文献
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Back Cover: Large‐Scale Synthesis of Helicene‐Like Molecules for the Design of Enantiopure Thin Films with Strong Chiroptical Activity (Chem. Eur. J. 10/2016) 下载免费PDF全文