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61.
Paulina Molinska Dr. Andrew Tarzia Dr. Louise Male Prof. Kim E. Jelfs Dr. James E. M. Lewis 《Angewandte Chemie (International ed. in English)》2023,62(51):e202315451
Metal-organic cages (MOCs) are popular host architectures assembled from ligands and metal ions/nodes. Assembling structurally complex, low-symmetry MOCs with anisotropic cavities can be limited by the formation of statistical isomer libraries. We set out to investigate the use of primary coordination-sphere engineering (CSE) to bias isomer selectivity within homo- and heteroleptic PdnL2n cages. Unexpected differences in selectivities between alternative donor groups led us to recognise the significant impact of the second coordination sphere on isomer stabilities. From this, molecular-level insight into the origins of selectivity between cis and trans diastereoisomers was gained, highlighting the importance of both host–guest and host-solvent interactions, in addition to ligand design. This detailed understanding allows precision engineering of low-symmetry MOC assemblies without wholesale redesign of the ligand framework, and fundamentally provides a theoretical scaffold for the development of stimuli-responsive, shape-shifting MOCs. 相似文献
62.
Strong heterodimeric interactions of phenylboronic acids with l-proline or betaine are evident in the solid state. The interaction energy is over 23 kcal/mol (at MP2/6-31+G∗). 相似文献
63.
We derive simple formulas for the higher-order moments of the quadrature operators operators of a two-field superposition by introducing a new generalized characteristic function depending on two complex variables. Using this formalism we investigate the preservation of higher-order squeezing during weak thermalization of an even coherent state. 相似文献
64.
Zygmuntowicz Justyna Wiecinska Paulina Miazga Aleksandra Konopka Katarzyna Szafran Mikolaj Kaszuwara Waldemar 《Journal of Thermal Analysis and Calorimetry》2018,133(1):303-312
Journal of Thermal Analysis and Calorimetry - Composite material with a gradient concentration of the metallic phase was prepared by the novel gel-centrifugal casting method. This method combines... 相似文献
65.
66.
Periodica Mathematica Hungarica - We examine the ideals of nowhere dense sets in three topologies on the set of positive integers, namely Furstenberg’s, Rizza’s and the common division... 相似文献
67.
Up to ~1 mol % maximum solid solubility of KNO2 or NaNO3, the two solid—solid transition temperatures in NaNO2-base alloys decrease ~11±4 deg per mol % solute, except that the upper transition temperature is hardly altered by alloying with KNO2. From the data on alloys with KNO2, the ratio of the entropy of the upper transition to the lower transition in NaNO2 is estimated as 0.35±0.07. 相似文献
68.
Dominiak PM Filarowski A Hansen PE Woźniak K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(16):4758-4766
We have analyzed deuterium isotope effects on (13)C chemical shifts in a series of o-hydroxy Schiff bases by applying factor analysis. Two orthogonal factors were obtained that explain about 80 and 10 % of the variance of the data. The numerical values of these factors can be related to 1H NMR chemical shifts of the proton involved in the intramolecular bonds delta(XH) (X = O or N). Such a relation allows one to identify clusters of compounds with different tautomeric forms of hydrogen bonding. Application of a similar approach to solution 13C NMR chemical shifts produces three important factors, which have a different structure to factors describing isotope effects. This illustrates well the different nature of chemical shifts and isotope effects. The three factors explain about 54, 15, and 13 % of variance. They can be rationalized and are strongly related to the electronic properties and location of substituents. 相似文献
69.
The reactions of 2,4-dinitrophenyl and 2,4,6-trinitrophenyl methyl carbonates (DNPC and TNPC, respectively) and S-(2,4-dinitrophenyl) and S-(2,4,6-trinitrophenyl) ethyl thiolcarbonates (DNPTC and TNPTC, respectively) with a series of benzenethiolate anions were subjected to a kinetic investigation in water, at 25.0 degrees C, and an ionic strength of 0.2 M (KCl). These reactions obey pseudo-first-order kinetics, under excess of benzenethiolate, and are first order in the latter reactant. However, comparable reactant concentrations were used in the reactions of 4-nitrobenzenethiolate anion with TNPC and TNPTC, which showed second-order kinetics. The nucleophilic rate constants are pH independent, except those for the reactions of TNPC with 4-methoxy- and pentafluorobenzenethiolates, and TNPTC with benzenethiolate and 4-chloro- and 3-chlorobenzenethiolates, which show acid dependence. The Br?nsted-type plots for the nucleophilic rate constants are linear with slopes beta = 0.9, 1.0, 0.9, and 0.9 for the reactions of DNPC, TNPC, DNPTC, and TNPTC, respectively. No break in the Br?nsted plot was found for the reactions of DNPC and DNPTC at pK(a) ca. 4.1 and 3.4, respectively, consistent with concerted mechanisms. TNPC is more reactive toward benzenethiolate anions than DNPC, and TNPTC more than DNPTC due to the better leaving groups involved. Comparison of the kinetic results obtained in this work with those for the concerted phenolysis of the same substrates shows that benzenethiolate anions are better nucleophiles toward carbonates than isobasic phenoxide anions. This is explained by Pearson's "hard and soft acids and bases" principle. 相似文献
70.
Jadwiga Szydłowska Paulina Krzyczkowska Piotr Gniewek Damian Pociecha Adam Krówczyński 《Liquid crystals》2013,40(11):1558-1570
Series of new Ni(II) metalomesogens of triangular molecular shape and forming Colh liquid crystalline (LC) phase were synthesised and described. Using in the molecular core the barbituric moieties that contain carbonyl or thiocarbonyl groups causes strong polarisation of the molecules and creates a permanent dipole moment μ, which was confirmed by quantum mechanical calculations. The relationship between molecular dipole moment and self-organisation of molecules into the columnar phase was considered. The position of alkyl and alkoxy chains substituted at phenyl ring that affects LC phase formation seems to be connected with planar conformation of the attached chains. These can broaden the mesogenic core and stabilise the Colh mesophase. 相似文献