223 research outputs found
Triplet energy management between two signaling units through cooperative rigid scaffolds
[EN] Through-bond triplet exciplex formation in donor-acceptor systems linked through a rigid bile acid scaffold has been demonstrated on the basis of kinetic evidence upon population of the triplet acceptors (naphthalene, or biphenyl) by through-bond triplet-triplet energy transfer from benzophenone.Financial support from the Spanish Government (Grants SEV-2012-0267, CTQ2012-38754-C03-03, CTQ2013-47872-C2-1-P and JCI-2011-09926), EU (PCIG12GA-2012-334257), Generalitat Valenciana (Prometeo Program), and Technical University of Valencia (VLC/Campus, ASIC-UPV for computational facilities and Predoctoral FPI fellowship for P. Miro) is gratefully acknowledged.MirĂł Richart, P.; VayĂĄ PĂ©rez, I.; Sastre Navarro, GI.; JimĂ©nez Molero, MC.; MarĂn GarcĂa, ML.; Miranda Alonso, MĂ. (2016). Triplet energy management between two signaling units through cooperative rigid scaffolds. Chemical Communications. 52(4):713-716. https://doi.org/10.1039/c5cc08102eS71371652
A Combined ComputationalâExperimental Study of the Kinetics of Intramolecular DielsâAlderReactions in a Series of 1,3,8-Nonatrienes
Activation enthalpies for a series of five 1,3,8-nonatriene intramolecular DielsâAlder (IMDA) reactions involving substrates 1â5 have been determined experimentally and Singletonâs natural abundance method has been employed to determine kinetic isotope effects in the IMDA reaction of fumarate 3. The activation enthalpies for the IMDA reactions of the systems possessing a âCH2OCH2â diene/dienophile tether are significantly smaller than their counterparts possessingthe âCH2OC(ÂŒO)â tether. The experimental activation enthalpies have been used to benchmark computed values from four model chemistries, namely two density functional theory functionals, B3LYP and M06-2X, and two generally very accurate composite ab initio wave function methods, CBS-QB3 and G4(MP2). G4(MP2) outperformed the computationally more expensive CBS-QB3 method, but the vastly cheaper M06-2X/6-31G(d)//B3LYP/6-31G(d) method was sufficiently accurate to be the recommended method of choice for calculating activation parameters. Experimental 2H kinetic isotope effects for the IMDA reaction of fumarate 3 confirmed the computational predictions that this DielsâAlder reaction is concerted but asynchronous
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