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11.
Nicolaides A 《Journal of the American Chemical Society》2003,125(30):9070-9073
A prerequisite for a stable singlet hydrocarbon carbene is the existence of high barriers toward isomerization. Four derivatives of cyclopentylidene (1-4) with rigid and varying carbon cages are examined computationally at the B3LYP/6-311+G(d,p) level of theory. Singlet ground states are predicted for carbenes 1-4, with DeltaE(ST)'s = 7-22 kcal/mol. The rearrangement paths considered are 1,3-hydrogen shift, 1,2-carbon shift and beta-CC bond-cleavage. Carbenes 3 and 4 lie in relatively shallow potential-energy wells (around 4 and 6 kcal/mol, respectively) and are expected to rearrange via 1,3-hydrogen shifts to cyclopropane derivatives. For 1 and 2, the lowest energy rearrangement path is beta-CC bond-cleavage requiring about 12 and 20 kcal/mol, respectively, placing 2 in the deepest potential-energy well among the four carbenes. 相似文献
12.
Dr. Athanassios K. Boudalis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(24):7022-7042
Spin triangles, that is, triangular complexes of half-integer spins, are the oldest molecular nanomagnets (MNMs). Their magnetic properties have been studied long before molecular magnetism was delineated as a research field. This Review presents the history of their study, with references to the parallel development of new experimental investigations and new theoretical ideas used for their interpretation. It then presents an indicative list of spin-triangle families to illustrate their chemical diversity. Finally, it makes reference to recent developments in terms of theoretical ideas and new phenomena, as well as to the relevance of spin triangles to spintronic devices and new physics. 相似文献
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14.
A New Approach for the Photosynthetic Antenna–Reaction Center Complex with a Model Organized Around an s‐Triazine Linker
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Susanne Kuhri Dr. Georgios Charalambidis Prof. Panagiotis A. Angaridis Prof. Theodore Lazarides Dr. Georgia Pagona Dr. Nikos Tagmatarchis Prof. Dr. Athanassios G. Coutsolelos Prof. Dr. Dirk M. Guldi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(7):2049-2057
Two new artificial mimics of the photosynthetic antenna‐reaction center complex have been designed and synthesized (BDP‐H2P‐C60 and BDP‐ZnP‐C60). The resulting electron‐donor/acceptor conjugates contain a porphyrin (either in its free‐base form (H2P) or as Zn‐metalated complex (ZnP)), a boron dipyrrin (BDP), and a fulleropyrrolidine possessing, as substituent of the pyrrolidine nitrogen, an ethylene glycol chain terminating in an amino group C60‐X‐NH2 (X=spacer). In both cases, the three different components were connected by s‐triazine through stepwise substitution reactions of cyanuric chloride. In addition to the facile synthesis, the star‐type arrangement of the three photo‐ and redox‐active components around the central s‐triazine unit permits direct interaction between one another, in contrast to reported examples in which the three components are arranged in a linear fashion. The energy‐ and electron‐transfer properties of the resulting electron‐donor/acceptor conjugates were investigated by using UV/Vis absorption and emission spectroscopy, cyclic voltammetry, and femtosecond transient absorption spectroscopy. Comparison of the absorption spectra and cyclic voltammograms of BDP‐H2P‐C60 and BDP‐ZnP‐C60 with those of BDP‐H2P, BDP‐ZnP and BDP‐C60, which were used as references, showed that the spectroscopic and electrochemical properties of the individual constituents are basically retained, although some appreciable shifts in terms of absorption indicate some interactions in the ground state. Fluorescence lifetime measurements and transient absorption experiments helped to elucidate the antenna function of BDP, which upon selective excitation undergoes a rapid and efficient energy transfer from BDP to H2P or ZnP. This is then followed by an electron transfer to C60, yielding the formation of the singlet charge‐separated states, namely BDP‐H2P .+‐ C60 .? and BDP‐ZnP .+‐ C60 . ?. As such, the sequence of energy transfer and electron transfer in the present models mimics the events of natural photosynthesis. 相似文献
15.
Nikolakopoulos Athanassios Ganas Ioannis 《Central European Journal of Operations Research》2017,25(3):587-609
Central European Journal of Operations Research - The paper proposes an economic model predictive control (EMPC) strategy for the inventory routing problem under demand uncertainty. The strategy is... 相似文献
16.
Samy Chammaa Dr. Bianca Sperl Anke G. Roth Aybike Yektaoglu Steffen Renner Dr. Thorsten Berg Prof. Dr. Christoph Arenz Prof. Dr. Athanassios Giannis Prof. Dr. Tudor I. Oprea Dr. Daniel Rauh Dr. Markus Kaiser Dr. Herbert Waldmann Prof. Dr. 《Angewandte Chemie (International ed. in English)》2010,49(21):3666-3670
17.
Athanassios G. Kartsatos Igor V. Skrypnik 《Transactions of the American Mathematical Society》2002,354(4):1601-1630
The purpose of this paper is to demonstrate that it is possible to define and compute the index of an isolated critical point for densely defined operators of type acting from a real, reflexive and separable Banach space into This index is defined via a degree theory for such operators which has been recently developed by the authors. The calculation of the index is achieved by the introduction of a special linearization of the nonlinear operator at the critical point. This linearization is a new tool even for continuous everywhere defined operators which are not necessarily Fréchet differentiable. Various cases of operators are considered: unbounded nonlinear operators with unbounded linearization, bounded nonlinear operators with bounded linearization, and operators in Hilbert spaces. Examples and counterexamples are given in 2,$"> illustrating the main results. The associated bifurcation problem for a pair of operators is also considered. The main results of the paper are substantial extensions and improvements of the classical results of Leray and Schauder (for continuous operators of Leray-Schauder type) as well as the results of Skrypnik (for bounded demicontinuous mappings of type Applications to nonlinear Dirichlet problems have appeared elsewhere.
18.
A detailed exploration of the configurational and conformational space of chloro- and bromo-hydroxyformaldoximes, Xhfaox (X = Cl, Br) has been carried out with the aid of the B3LYP level of density functional theory, using the 6-31G(d,p) basis set. The most stable configuration in each series of the Clhfaox and Brhfaox conformers corresponds to the Z-s-cis, s-trans configuration, while the highest energy Z-(s-trans, s-cis) conformers were found at 7.0(7.6) and 6.0(6.6) kcal mol(-1), respectively, at the B3LYP(QCISD(T)) levels of theory. Saddle points were also located on the PES of the Clhfaox and Brhfaox compounds corresponding to Z-(s-cis, s-cis) conformers at 13.8(14.9) and 13.6(14.6) kcal mol(-1), respectively, at the B3LYP(QCISD(T)) levels. Upon dehydration Xhfaox could afford a number of isomeric CXNO species. The dehydration processes of Xhfaox are predicted to be endothermic, the computed heats of reactions found in the range of 20.5 to 86.2 kcal mol(-1) and 15.9 to 100.4 kcal mol(-1) at the B3LYP and QCISD(T) levels, respectively. The reaction pathways for the addition of water to halo-fulminates yielding the most stable Xhfaox conformers was predicted to be concerted with a single transition structure, but are asynchronous with activation barriers of 32.8 and 43.0 kcal mol(-1) for the chloro- and bromo-derivatives, respectively. The PES governing the isomerization reactions of the CXNO isomers have also been calculated, and possible isomerization pathways have been delineated. Upon dehydrohalogenation the Xhfaox conformers yield hydroxy-isocyanate or hydroxy-fulminate, the former being more stable by 31.8(18.8) kcal mol(-1) at the B3LYP(QCISD(T)) levels of theory. The reaction pathways for the addition of HX to hydroxy-isocyanate were predicted to be slightly exothermic, the heats of reactions being -3.2 and -5.5 kcal mol(-1), respectively, and have to surmount high activation barriers of 39.7 and 35.0 kcal mol(-1), respectively. Similarly, the addition of HX to hydroxy-fulminate was predicted to be much more exothermic, the heats of reactions being -34.7 and -37.3 kcal mol(-1), respectively, and have to surmount much lower activation barriers of only 10.5 and 7.5 kcal mol(-1) respectively, at the B3LYP level. Finally, calculated structures, relative stability, and bonding properties of all stationary points located on the PES of the systems and reactions studied are thoroughly discussed with respect to computed electronic properties. 相似文献
19.
20.
The 1:1 equisized hard-sphere electrolyte or restricted primitive model has been simulated via grand-canonical fine-discretization Monte Carlo. Newly devised unbiased finite-size extrapolation methods using loci in the temperature-density or (T,rho) plane of isothermal rho(2-k) vs pressure inflections, of Q identical with(2)/ maxima, and of canonical and C(V) criticality, yield estimates of (T(c),rho(c)) to +/-(0.04,3)%. Extrapolated exponents and Q ratio are (gamma,nu,Q(c)) = [1.24(3), 0.63(3); 0.624(2)], which support Ising (n = 1) behavior with (1.23(9), 0.630(3); 0.623(6)), but exclude classical, XY (n = 2), self-avoiding walk (n = 0), and n = 1 criticality with potentials varphi(r)>Phi/r(4.9) when r-->infinity. 相似文献