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Dudekula Sharmila K. Yuvaraj Subrat Kumar Barik Dipak Kumar Roy Kiran Kumarvarma Chakrahari Rongala Ramalakshmi Bijan Mondal Dr. Babu Varghese Prof. Sundargopal Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(45):15219-15225
The synthesis, structural characterization, and reactivity of new bridged borylene complexes are reported. The reaction of [{Cp*CoCl}2] with LiBH4 ? THF at ?70 °C, followed by treatment with [M(CO)3(MeCN)3] (M=W, Mo, and Cr) under mild conditions, yielded heteronuclear triply bridged borylene complexes, [(μ3‐BH)(Cp*Co)2(μ‐CO)M(CO)5] ( 1 – 3 ; 1 : M=W, 2 : M=Mo, 3 : M=Cr). During the syntheses of complexes 1 – 3 , capped‐octahedral cluster [(Cp*Co)2(μ‐H)(BH)4{Co(CO)2}] ( 4 ) was also isolated in good yield. Complexes 1 – 3 are isoelectronic and isostructural to [(μ3‐BH)(Cp*RuCO)2(μ‐CO){Fe(CO)3}] ( 5 ) and [(μ3‐BH)(Cp*RuCO)2(μ‐H)(μ‐CO){Mn(CO)3}] ( 6 ), with a trigonal‐pyramidal geometry in which the μ3‐BH ligand occupies the apical vertex. To test the reactivity of these borylene complexes towards bis‐phosphine ligands, the room‐temperature photolysis of complexes 1 – 3 , 5 , 6 , and [{(μ3‐BH)(Cp*Ru)Fe(CO)3}2(μ‐CO)] ( 7 ) was carried out. Most of these complexes led to decomposition, although photolysis of complex 7 with [Ph2P(CH2)nPPh2] (n=1–3) yielded complexes 9 – 11 , [3,4‐(Ph2P(CH2)nPPh2)‐closo‐1,2,3,4‐Ru2Fe2(BH)2] ( 9 : n=1, 10 : n=2, 11 : n=3). Quantum‐chemical calculations by using DFT methods were carried out on compounds 1 – 3 and 9 – 11 and showed reasonable agreement with the experimentally obtained structural parameters, that is, large HOMO–LUMO gaps, in accordance with the high stabilities of these complexes, and NMR chemical shifts that accurately reflected the experimentally observed resonances. All of the new compounds were characterized in solution by using mass spectrometry, IR spectroscopy, and 1H, 13C, and 11B NMR spectroscopy and their structural types were unequivocally established by crystallographic analysis of complexes 1 , 2 , 4 , 9 , and 10 . 相似文献
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Suman Kumar Saha Rajib Kar Durbadal Mandal Sakti Prasad Ghoshal 《Memetic Computing》2013,5(4):311-321
In this paper, a new optimization method named gravitational search algorithm (GSA) is adopted for designing optimal linear phase finite impulse response band pass (BP) and band stop (BS) digital filters. Other various population based evolutionary algorithms like real coded genetic algorithm, conventional particle swarm optimization, differential evolution (DE), bee swarm optimization have also been applied for the sake of comparative study of the same optimal designs. In GSA, particles are considered as objects and their performances are measured by their masses. All these objects attract each other by gravity forces, and these forces produce global movements of all objects towards the objects with heavier masses. GSA guarantees the exploitation step of the algorithm and it is apparently free from premature convergence. Extensive simulation results justify superior optimization capability of GSA over the afore-mentioned optimization techniques for the solution of the multimodal, non-differentiable, highly non-linear, and constrained filter design problems. 相似文献
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Sangeeta Mondal Sakti Prasad Ghoshal Rajib Kar Durbadal Mandal 《Journal of Optimization Theory and Applications》2012,155(1):315-324
This paper proposes one novel algorithm called differential evolution with wavelet mutation for the optimal design of linear phase finite impulse response filters. For comparative performance study, the Parks–McClellan algorithm and some evolutionary algorithms like the real coded genetic algorithm, conventional particle swarm optimization, and conventional differential evolution have also been applied. 相似文献
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Kuruva Balanna Soumen Barik Sayan Shee Rajesh G. Gonnade Akkattu T. Biju 《Chemical science》2022,13(39):11513
The ubiquity of ε-lactones in various biologically active compounds inspired the development of efficient and enantioselective routes to these target compounds. Described herein is the enantioselective synthesis of indole-fused ε-lactones by the N-heterocyclic carbene (NHC)-Lewis acid cooperative catalyzed dynamic kinetic resolution (DKR) of in situ generated γ,γ-disubstituted indole 2-carboxaldehydes. The Bi(OTf)3-catalyzed Friedel–Crafts reaction of indole-2-carboxaldehyde with 2-hydroxy phenyl p-quinone methides generates γ,γ-disubstituted indole 2-carboxaldehydes, which in the presence of NHC and Bi(OTf)3 afforded the desired tetracyclic ε-lactones in up to 93% yield and >99 : 1 er. Moreover, preliminary studies on the mechanism of this formal [4 + 3] annulation are also provided.NHC-Lewis acid cooperative catalyzed dynamic kinetic resolution (DKR) of transiently generated γ,γ-disubstituted indole 2-carboxaldehydes leading to the enantioselective synthesis of tetracyclic ε-lactones is reported. 相似文献