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1.
In this paper we have reviewed the theoretical framework of the coupled-cluster (cc) based linear response model as a tool
for directly calculating energy differences of spectroscopic interest like excitation energy (ee), ionisation potential (ip)
or electron affinity (ea). In this model, the ground state of a many-electron system is described as in a coupled cluster
theory for closed shells. The electronic ground state is supposed to interact with an external photon field of frequencyw, and the poles of the linear response function as a function ofw furnish with the elementary excitations of the system. Depending on the general form of the coupling term chosen, appropriate
difference energies like ee, ip or EA may be generated. Pertinent derivations of the general working equations are reviewed,
and specific details as well as approximations for ee, ip or ea are indicated. It is shown that the theory bears a close resemblance
to the equation of motion (eom) method but is superior to the latter in that the ground state correlation is taken to all orders and may be looked upon
as essentially a variant of renormalisedtda. A perturbative analysis elucidating the underlying perturbative structure of the formulation is also given which reveals
that the theory has a hybrid structure: the correlation terms are treated akin to an open shellmbpt, while the relaxation terms are treated akin to a Green function theory. A critique of the methodvis-a-vis other cc-based approaches for difference energies forms the concluding part of our review. 相似文献
2.
Arijit BanerjeeSamir Kumar Maji Michael G.B. DrewDebasish Haldar Arindam Banerjee 《Tetrahedron letters》2003,44(4):699-702
A single-crystal X-ray diffraction study of the terminally protected tetrapeptide Boc-β-Ala-Aib-Leu-Aib-OMe 1 (Aib: α-aminoisobutyric acid; β-Ala: β-Alanine) reveals that it adopts a new type of double turn structure which self-associates to form a unique supramolecular helix through intermolecular hydrogen bonds. Scanning electron microscopic studies show that peptide 1 exhibits amyloid-like fibrillar morphology in the solid state. 相似文献
3.
A highly functionalized cyclopentanone building block 13 was prepared by a facile Rh-catalyzed intramolecular CH insertion reaction of an enantiopure α-diazo-γ-hydroxy-β-ketosulfone 12, in turn derived from an α-hydroxy acid 2. A cyclic γ-hydroxy vinyl sulfone 16 was also prepared from 13. 相似文献
4.
Indole-2-yl-prop-2-ynyl sulfides, under thiophenol-mediated alkenyl radical cyclization conditions, afforded exclusively 4-thiophenyl-2,3,4,9-tetrahydrothiopyrano[2,3-b]indoles or 3-thiophenylmethyl-2,3,8-trihydrothieno[2,3-b]indoles depending on the substituent at the indole nitrogen. 相似文献
5.
Chloramphenicol and thiamphenicol have been enantioselectively synthesized using an asymmetric halohydrin reaction as a key step. In particular, halomethoxylation reaction was used, where O-methyl functions as a hydroxyl protecting group and eliminates an additional protection step. 相似文献
6.
Chemical synthesis of the trisaccharide of the steroid glycoside Sokodoside B isolated from Erylus placenta is reported. Stereoselective, high-yielding glycosylation strategies through thioglycoside activation using H2SO4 immobilized on silica in conjunction with N-iodosuccinimide are used for better results. A late stage TEMPO-mediated oxidation was performed for the formation of required uronic acid moiety. An analog of the target trisaccharide is also prepared by using a bis-glycosylation approach. 相似文献
7.
Samik Gupta Anil Kumar Barik Sachindranath Pal Arijit Hazra Somnath Roy Ray J. Butcher Susanta Kumar Kar 《Polyhedron》2007
Four cis-dioxomolybdenum complexes of general formula [MoO2(Ln)EtOH] (n = 1–4) and one oxomolybdenum(IV) complex [MoO(L4)EtOH], with potentially tridentate Schiff bases derived from 5-methyl pyrazole-3-carbohydrazide and salicylaldehyde/substituted salicylaldehyde/o-hydroxy acetophenone have been prepared. The Mo(IV) complex is derived from the Mo(VI) dioxo complex by oxotransfer reaction with PPh3. The complexes are characterized by elemental analysis, electronic spectra, IR, 1H NMR, and by cyclic voltammetry. All the Mo(VI) species are crystallographically characterized. The complexes have a distorted octahedral structure in which the ligand behaves as a binegative donor one, leaving the pyrazole –N uncoordinated towards the metal center. It is also revealed from the crystal structure that the Mo(VI) center enjoys an NO5 donor environment. 相似文献
8.
Dr. Papri Sutar Dr. Vasudeva Rao Bakuru Pooja Yadav Subhajit Laha Dr. Suresh Babu Kalidindi Prof. Dr. Tapas Kumar Maji 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(10):3268-3272
The composite hydrogel of a nanoscale metal–organic framework (NMOF) and nanoclay has emerged as a new soft-material with advanced properties and applications. Herein, we report a facile synthesis of a hydrogel nanocomposite by charge-assisted self-assembly of Pd@ZIF-8 nanoparticles with Laponite® nanoclay which coat the surface of Pd@ZIF-8 nanoparticles. Such surface coating significantly enhanced the thermal stability of the ZIF-8 compared to the pristine framework. Further, the Pd@ZIF-8+LP hydrogel nanocomposite shows better size-selective catalytic hydrogenation of olefins than Pd@ZIF-8 nanoparticles based on selective diffusion of the substrate. 相似文献
9.
10.
Ovender Singh Priyanka Gupta Anshu Singh Ankur Maji Udai P. Singh Kaushik Ghosh 《应用有机金属化学》2019,33(5)
Hexacoordinated non‐heme iron complexes [FeII(L1)2](ClO4)2 ( 1 ) and [FeII(L2)2](PF6)2 ( 2 ) have been synthesized using ligands L1 = (E)‐2‐chloro‐6‐(2‐(pyridin‐2ylmethylene) hydrazinyl)pyridine and L2 = (E)‐2‐chloro‐6‐(2‐(1‐(pyridin‐2‐yl)ethylidene)hydrazinyl) pyridine]. These complexes are highly active non‐heme iron catalysts to catalyze the C (sp3)?H bonds of alkanes. These iron complexes have been characterized using ESI?MS analysis and molecular structures were determined by X‐ray crystallography. ESI ? MS analysis also helped to understand the generation of intermediate species like FeIII?OOH and FeIV=O. DFT and TD?DFT calculations revealed that the oxidation reactions were performed through high‐valent iron center and a probable reaction mechanism was proposed. These complexes were also utilized for the degradation of orange II and methylene blue dyes. 相似文献