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231.
Kiran Bharadwaj Himanshu Choudhary Dr. Soumitra Hazra Dr. Subhadip Ghosh 《Chemphyschem》2020,21(5):415-422
Photoinduced electron transfer (PET) from N-methylaniline (NMA) to a photoexcited CdTe quantum dot (QD*) is studied in toluene. The PET mechanism at low to moderate quencher (NMA) concentrations (<0.08 M) remains mostly collisional with some contributions from QD-NMA complex formation. However, at high quencher concentrations (>0.10 M), QDs form larger numbers of static complexes with NMA molecules leading to a steep positive deviation in the steady-state Stern–Volmer curves. An isothermal titration calorimetry (ITC) study confirms the formation of QD-NMA complexes (K∼150 M−1) at high quencher concentrations. Fitting our experimental data using a stochastic kinetic model indicates that the number of NMA molecules attached per QD at highest NMA concentration (∼0.16 M) used in this study decreases from ∼0.76 to ∼0.47 with reducing the QD size from ∼5.2 nm to ∼3.2 nm. However, the PET rate increases with decreasing QD size, which is commensurate with the observation that the chemical driving force (ΔG) increases with decreasing the QD particle size. We have analyzed the PET kinetics mainly by using Stern-Volmer fittings. However, in some cases Tachiya's stochastic kinetic model is used for stoichiometric analysis, which seems to be useful only at high quencher concentrations. The measured PET rate coefficients in all the cases are found to be at least an order of magnitude lower when compared to the diffusion-controlled rate of the reaction medium. 相似文献
232.
Dr. Joydeb Goura Dr. Bassem S. Bassil Dr. Jasleen K. Bindra Dr. Iwona A. Rutkowska Prof. Pawel J. Kulesza Prof. Naresh S. Dalal Prof. Ulrich Kortz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(68):15821-15824
The 48-FeIII-containing 96-tungsto-16-phosphate, [FeIII48(OH)76(H2O)16(HP2W12O48)8]36− ( Fe48 ), has been synthesized and structurally characterized. This polyanion comprises eight equivalent {FeIII6P2W12} units that are linked in an end-on fashion forming a macrocyclic assembly that contains more iron centers than any other polyoxometalate (POM) known to date. The novel Fe48 was synthesized by a simple one-pot reaction of an {Fe22} coordination complex with the hexalacunary {P2W12} POM precursor in water. The title polyanion was characterized by single-crystal XRD, FTIR, TGA, magnetic and electrochemical studies. 相似文献
233.
Ankita Singh Vipin K. Maikhuri Vineet Verma Rajni Johar Chhatwal Deepti Sharma 《合成通讯》2020,50(18):2787-2795
AbstractHere in, the condensation of boc-glycine with 2,6-anhydro-3,4,5-tri-O-benzyl-D-gluco-heptitol followed by its boc-deprotection to form 2,6-anhydro-3,4,5-tri-O-benzyl-D-gluco-heptitolyl bis-glycinate, which in turn on condensation with succinic acid/pyridine-2,6-dicarboxylic acid led to the formation of sugar-amino acid hybrid macrocyclic compounds 4, 6 and debenzylated marocyclic compound 5, having amide bonds that function as efficient host for polar, hydrogen bond acceptors and carboxylate ions. The anion inclusion capability of synthesized macrocylic hosts has been evaluated by the study of their binding with boc-GlyCOOˉ anion as guest through 1H NMR titration studies in CDCl3. The binding constant (Ka) of boc-GlyCOOˉ guest with macrocyclic hosts 4 and 6 involving succinate and pyridine-2,6-dicarboxylate linkers was found to be 9.201?×?103 and 1.437?×?104 M?1, respectively. The higher binding constant was observed in the complex of boc-GlyCOOˉ with pyridine-dicarboxylate containing host may be due to the extra rigidity & suitable conformation attained by the presence of rigid-aromatic dicarboxylate linker. 相似文献
234.
Three switchable macrocycles based on photochromic dithienylethene were synthesized under the template of dibenzylammonium hexafluorophosphate. Their structure were well-confirmed by NMR, ESI-MS and X-ray diffraction. Their photochromism indicated that they showed good reversibility in solution. Additionally, the theoretical calculation suggested that photoirradiation can change the cavity of macrocycles. 相似文献
235.
一种大环化合物的晶体结构及其双核铜配合物的酪氨酸酶活性研究 总被引:2,自引:0,他引:2
A ring-contracted form macrocycle, 29,30-dioxo-3,6,9,17,20,23,29,30-octaazapentacyclo[23,3,1,1^11,15,0^2,6,0^16,20]-triacontaneocta- 1 (28),9,11 (12), 13,15(30),23,25(29),26-ene (L) was synthesized by condensation of diethyltriamine with pyridine-1-oxide-2,6-dicarboxaldehyde. A porous three-dimensional layer structure in its crystal was formed by self-assembly through hydrogen bonds and π-π interaction. Its dinuclear copper(I) complex [Cu2L(MeOH)2]-(BF4)2*2H2O and dinuclear-copper(II) complex [Cu2L(MeOH)2](ClO4)4*2H2O were obtained and could oxidize catalytically four phenolic substrates hydroquinone, 2-methyl-hydroquinone, 2,6-di-tert-butylphenol and 2,6-dimethylphenol, in a mixture of methanol and acetonitrile (V : V, 4 : 1). The copper(I) complex reacted with dioxygen to form an oxygenated species as an initial active intermediate for oxidation of the phenols. Oxidation of the substrates by the copper(II) complex produced a copper(I) complex and the oxidation products of the substrates. 相似文献
236.
合成了三种锰(Ⅱ)配合物,通过多种物理方法进行了表征,推断了它们的结构式。用核黄素光照法测定了它们的超氧化物歧化酶活性,并对其清除多形核白细胞(PMNL)呼吸爆发产生的活性氧及黄嘌呤与黄嘌呤氧化酶体系产生的·O2-及H2O2-Fe2+产生的·OH的效能进行了研究,结果表明能降低活性氧导致的鲁米诺化学发光值;降低·O2-与DMPO加合物的ESR波谱信号,减少·O2-损伤膜提取物产生的脂类过氧化物产量;对·OH与DMPO加合物的ESR波谱无影响,说明这三种配合物确具有SOD样活性。 相似文献
237.
Qingqi ChenDavid Dolphin 《Tetrahedron》2003,59(6):871-875
Cyclooctapyrroles, novel macrocycles containing two biladiene-a,c units, were synthesized in high yield from the condensation of 3,3′-dipyrromethanes with 5,5′-diformyl-2,2′-dipyrromethane under acidic conditions. These macrocycles form dinuclear complexes with zinc(II). 相似文献
238.
Novel phosphorus-containing polyoxamacrocycles with one to two reactive thiophosphoryl chloride groups 5, 6, 7, 8 were synthesized from bishydroxyl compounds 1, 2, 3, 4 and thiophosphoryl chloride respectively. Their structures were confirmed by ^ 1H NMR, ^13C NMR, ^31p NMR and elemental analysis. 相似文献
239.
Kraig A. Wheeler Travis R. Helgren Thomas W. Clayton 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(3):306-311
The title bimolecular structure, [Cu4Cl6O(C4H8O)3(H2O)]2[Cu4Cl6O(C4H8O)4]·4C4H8O, at 100 K has monoclinic (P21/c) symmetry. The structure contains nine symmetry‐independent molecules expressed in simplest molecular form as 6[Cu4Cl6O(C4H8O)3(H2O)·2(C4H8O)]:3Cu4Cl6O(C4H8O)4. The compound exhibits a supercell (smaller than the unit cell based on weak reflections) structure due to pseudotranslational symmetry. The structure displays O—H...O hydrogen bonding between bound water ligands and tetrahydrofuran (THF) solvent molecules. The structure exhibits disorder for 12 of the THF molecules, of which seven are ligated to Cu and five are hydrogen bonded to H2O ligands. 相似文献
240.
Chuanzhi Sun Kui Wang Haitao Sun Nan Sun Dezhan Chen 《International journal of quantum chemistry》2014,114(12):769-781
The mechanism for initially divergent radical reactions reconverging to form a single product is studied using density functional theory calculations. The calculation results suggest that there are six possible pathways from reactants to products. The free energy barriers of the rate‐determining steps of each pathway are almost equal. Thus, different from usual reaction, the selectivity of this reaction is determined by the relative value of free energy barriers of the two competitive reactions, that is, cyclization and bimolecular trapping, rather than that of rate‐determining steps. In all reaction pathways, cyclization reaction is more competitive than bimolecular trapping reaction due to its low free energy barrier. In addition, the free energy barriers of bimolecular trapping reaction between Bu3SnH and reactants are all lower than that of NC? C6H11. However, Bu3SnH is not always suitable due to its large steric repulsion. © 2014 Wiley Periodicals, Inc. 相似文献