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71.
In this work the effect of the basis set superposition error (BSSE) is explored with the counterpoise method on the occupied and unoccupied Hartree-Fock (HF) and Kohn-Sham (KS) orbitals. Three different systems linked by hydrogen bonds, H(2)O...FH, H(2)O...H(2)O, and H(2)O...CFH(3), were studied by using the basis set families cc-pVXZ and aug-cc-pVXZ (X = D, T, Q). The basis sets were tested with the HF method and two approximations for the exchange-correlation functional of KS: a generalized gradient approximation and a hybrid approach. In addition to these methods, the second-order M?ller-Plesset perturbation theory, MP2, was considered. It was found that the presence of the "ghost" basis set affects the orbitals in two ways: (1) The occupied KS orbitals are more sensitive to the presence of this "ghost" basis set than the occupied HF orbitals. For this reason the BSSE observed in HF is less than that obtained with KS. (2) The unoccupied HF orbitals are more sensitive to the presence of the "ghost" basis set than their corresponding occupied orbitals. Because the MP2 method uses both, occupied and unoccupied HF orbitals, to compute the total energy, the contribution of the BSSE is bigger than that obtained with HF or KS methodologies. 相似文献
72.
A mild and new procedure for the selective cleavage of an alkoxycarbonyl group (Boc, CBz) in N,N-dicarbamoyl-protected amino compounds is described. The method is based on the use of lithium bromide in acetonitrile and is compatible with a large range of other functionalities present in the substrates. Compared with other reported methodologies, the procedure is particularly useful for the Cbz-selective cleavage in N,N-Ts,Cbz-diprotected amines. A rationalization of the selectivity supported by ab initio calculations is also presented. 相似文献
73.
E.p.r. spectra of [Cu(et2dtc)2], Na[Cu(asp/glut)(et2dtc)] and Na2[Cu(asp/glut)(et2dtc)2] in the polycrystalline state have
been recorded and discussed. The complexes display an antiferromagnetic exchange interaction, increasing in the order: Na2[Cu(asp/glut)(et2dtc)2]
< Na[Cu(asp/glut)(et2dtc)] < [Cu(et2dtc)2]
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
74.
75.
Summary Triisopropoxy bis(O,O-dialkyl dithiophosphates), (i-PrO)3M[S2P(OR)2]2 (M = Nbv, Tav; R = n-Pr, i-Pr, i-Bu and Ph) have been prepared by reacting the appropriate triisopropoxymetal(V)dichloride, (i-PrO)3MCl2 (1 mol) with sodium/ammonium dialkyl dithiophosphates (2 mols)in THF. The monomeric products which are viscous liquids, soluble in common organic solvents and highly susceptible to hydrolysis, were characterized by i.r. and n.m.r. spectra which indicate a bidentate mode of attachment of dithiophosphato groups to the metal. 相似文献
76.
Ghadwal Rajendra Singh Sharma Malti Singh Anirudh Mehrotra Ram C. 《Transition Metal Chemistry》2004,29(4):419-424
Complexes of the types VO(L)(R-deaH), VO(R-dea)(LH), and VO(L)(OGOH)[L = deprotonated form of N-(1-hydroxyethyl) naphthaldimine; R-dea = deprotonated form of a N-substituted diethanolamine, with R = H or Ph; G = CH2CH2, CHMeCHMe, CMe2CMe2, CHMeCH2CMe2, CMe2CH2CH2CMe2] have been prepared by the equimolar reactions of VO(OPr
i
)3, LH2, and an appropriate diethanolamine or glycol in benzene. All of these coloured solid complexes have been characterised by elemental (C, H, N, and V) analyses and by spectroscopic (i.r., electronic, 1H-, 51V-n.m.r) studies. The relative lability of the hydroxy group(s) of N-(1-hydroxyethyl)naphthaldiamine, diethanolamine, and glycol has also been investigated. 相似文献
77.
The reaction of the anticancer active compound [Rh(2)(mu-O(2)CCH(3))(2)(bpy)(2)(CH(3)CN)(2)][BF(4)](2) (1) (bpy = 2,2'-bipyridine) with NaC(6)H(5)S under anaerobic conditions yields Rh(2)(eta(1)-C(6)H(5)S)(2)(mu-C(6)H(5)S)(2)(bpy)(2).CH(3)OH (2), which was characterized by UV-visible, IR, and (1)H NMR spectroscopies as well as single-crystal X-ray crystallography. Compound 2 crystallizes as dark red platelets in the monoclinic space group C2/c with cell parameters a = 20.398(4) A, b = 11.861(2) A, c = 17.417(4) A, beta = 108.98 degrees, V = 3984.9(14) A(3), Z = 4. The main structural features are the presence of a [Rh(2)](4+) core with a Rh-Rh distance of 2.549(2) A bridged by two benzene thiolate ligands in a butterfly-type arrangement. The axial positions of the [Rh(2)](4+) core are occupied by two terminal benzene thiolates. Cyclic voltammetric studies of 2 reveal that the compound exhibits an irreversible oxidation at +0.046 V in CH(3)CN, which is in accord with the fact that the compound readily oxidizes in the presence of O(2). The fact that this unusual dirhodium(II/II) thiolate compound is formed under these conditions is an important first step in understanding the metabolism of dirhodium anticancer active compounds with thiol-containing peptides and proteins. 相似文献
78.
Alvarez-Puebla RA dos Santos DS Blanco C Echeverria JC Garrido JJ 《Journal of colloid and interface science》2005,285(1):41-49
Illite clays are known to have a strong affinity for metallic pollutants in the environment and can be applied as low-cost adsorbents for industrial waste treatment. A crucial factor in the development of such applications, however, is the understanding of the chemical, mineralogical, and colloidal properties of these clays. It is also important to understand the mechanisms involved in the surface adsorption of metals by these adsorbants. In order to study the retention of transition metals on illite clays, we have applied surface characterization techniques such as FPIA, SEM-EDX, XRD, N2 (77 K) adsorption, and FTIR. In addition to these experimental techniques, we have also employed a theoretical model that accounts for the chemistry of transition metal ions, and considers the global retention process to be the sum of several single retention processes. This model adequately fits the experimental data and allows for the speciation of metal retention on illite surfaces. Between pH values of 2.53 and 3.01 the only adsorption processes are the electrostatic sorption of [Cu(H2O)6]2+, and the surface complexation of [Cu(H2O)6]2+ and [Cu(OH)(H2O)5]+ ions. Surface complexation of [Cu(OH)(H2O)5]+ ions increases with pH, overcoming [Cu(H2O)6]2+ retention, and thus contributing to the surface precipitation of Cu(OH)2. 相似文献
79.
Bernabé-Pineda M Ramírez-Silva MT Tapia-Benavides R Rojas-Hernández A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(5):1071-1076
The importance assigned to chelating agents in diverse areas has impelled studies concerning their development as related to metal ions representing a biological concern. The synthesis of di-isopropyliminodiacetoamide (D) is presented in this work. The acidity constant obtained for D was pKa = 5.79 +/- 0.04 with the aid of program SUPERQUAD. The equilibrium constants for D with Cu(II) were obtained with the aid of program SQUAD for CuD2+ and CuD2(2)+ species giving log beta1 = 4.795 +/- 0.002 and log beta2 = 8.374 +/- 0.004, respectively. 相似文献
80.
Dr. Rebeca Arevalo Dr. Ramón López Prof. Larry R. Falvello Dr. Lucía Riera Dr. Julio Perez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(1):379-389
The reactions of [Re(N-N)(CO)3(PMe3)]OTf (N-N=2,2′-bipyridine, bipy; 1,10-phenanthroline, phen) compounds with tBuLi and with LiHBEt3 have been explored. Addition to the N-N chelate took place with different site-selectivity depending on both chelate and nucleophile. Thus, with tBuLi, an unprecedented addition to C5 of bipy, a regiochemistry not accessible for free bipy, was obtained, whereas coordinated phen underwent tBuLi addition to C2 and C4. Remarkably, when LiHBEt3 reacted with [Re(bipy)(CO)3(PMe3)]OTf, hydride addition to the 4 and 6 positions of bipy triggered an intermolecular cyclodimerization of two dearomatized pyridyl rings. In contrast, hydride addition to the phen analog resulted in partial reduction of one pyridine ring. The resulting neutral ReI products showed a varied reactivity with HOTf and with MeOTf to yield cationic complexes. These strategies rendered access to ReI complexes containing bipy- and phen-derived chelates with several C(sp3) centers. 相似文献