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11.
A new Ni4 distorted cubane complex [Ni4(μ3-OMe)4Q4(MeOH)4] (1) (where Q− is the anion of 8-quinolinol) is obtained from the reaction of NaQ with Ni(OAc)2 · 4H2O in refluxing MeOH via solvent derived μ3-OMe assisted self-assembly of four nickel(II) centres. The periphery of [Ni4(OMe)4] cubane is covered by four Q− and four MeOH molecules. This methanol specific reaction is not supported in solvent glycinol (Hgl; NH2(CH2)2OH), an amine substituted ethanol, producing monomeric [NiQ2(Hgl)2] · 2H2O (2 · 2H2O) instead and is able to cleave 1 to yield 2 · 2H2O. The cryomagnetic susceptibility data of powdered 1 can be modeled by a two J equation yielding J1 = −1.8(1) cm−1, J2 = 3.9(1) cm−1 and g = 2.24. 相似文献
12.
A variety of phosphorodiamidate compounds were synthesized from the corresponding phosphorodichloridate intermediates and phosphorus oxychloride. These were completely characterized using different spectroscopic methods and single crystal X-ray diffraction studies on one of them. Studies revealed that water in the presence of a mild Lewis acid like ZnCl2 was found to assist the hydrolysis of the P–N linkage. The proof of this concept was effectively realized through the hydrolysis of hexamethylphosphoramide. 相似文献
13.
Prasant Kumar Nanda Manindranath Bera Ana Maria da Costa Ferreira Armando Paduan-Filho Debashis Ray 《Polyhedron》2009,28(18):4065-4071
The reaction of Cu(ClO4)2·6H2O with dimethylglyoxime (H2dmg) in a 1:1 mole ratio in aqueous methanol at room temperature affords the dinuclear complex [Cu2(μ-Hdmg)4] (1). Reaction of 1 with [Cu(bpy)(H2O)2](ClO4)2 (bpy = 2,2′-bipyridine) in a 1:1 mole ratio in aqueous methanol at room temperature yields the tetranuclear complex [Cu4(μ-Hdmg)2(μ-dmg)2(bpy)2(H2O)2](ClO4)2 (2). The direct reaction of Cu(ClO4)2·6H2O with H2dmg and bpy in a 2:2:1 mole ratio in aqueous methanol at room temperature also yields 2 quantitatively. The complexes 1 and 2 were structurally characterized by X-ray crystallography. Unlike the binding in Ni/Co-dmg, two different types of N?O bridging modes during the oxime based metallacycle formation and stacking of square planar units have been identified in these complexes. The neutral dinuclear complex 1 has CuN4O coordination spheres and complex 2 consists of a dicationic [Cu4(μ-Hdmg)2(μ-dmg)2(bpy)2(H2O)2]2+ unit and two uncoordinated ClO4? anions having CuN4O and CuN2O3 coordination spheres. The two copper(II) ions are at a distance of 3.846(8) Å in 1 for the trans out of plane link and at 3.419(10) and 3.684(10) Å in 2 for the trans out of plane and cis in plane arrangements, respectively. The average Cu–Noxime distances are 1.953 and 1.935 Å, respectively. The average basal and apical Cu?Ooxime distances are 1.945, 2.295 and 2.429 Å. The UV–Vis spectra of 2 is similar to the spectrum of the reaction mixture of 1 and [Cu(bpy)(H2O)2]2+. Variable temperature magnetic properties measurement shows that the interaction between the paramagnetic copper centers in complex 1 is antiferromagnetic in nature. The EPR spectra of frozen solution of the complexes at 77 K consist of axially symmetric fine-structure transitions (ΔMS = 1) and half-field signals (ΔMS = 2) at ca. 1600 G, suggesting the presence of appreciable Cu–Cu interactions. 相似文献
14.
Sarkar M Aromí G Cano J Bertolasi V Ray D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(46):13825-13833
A high-spin Co(II) cluster with a rare pentagonal molecular structure and formula [Co(5)(CO(3))(2)(bpp)(5)]ClO(4) (1; Hbpp is 2,6-bis(phenyliminomethyl)-4-methylphenolate) has been synthesized and characterized by single-crystal X-ray diffraction. This topology arises from fusing five [Co(2)(bpp)] moieties in a cyclic manner around two CO(3)(2-) central ligands, resulting in propeller-like configuration. The irregular coordination of the carbonate ions to the metal centers results in a combination of coordination numbers (CNs) of the Co(II) ions of five and six. The bulk magnetization of this complicated magnetically exchanged system has been modeled successfully by employing a matrix diagonalization technique. For this, the combination of S=3/2 ions (CN=5) with ions exhibiting strong spin-orbit coupling (CN=6) has been considered and a perturbative approach to handle the data in the whole studied range of temperatures (2-300 K) yielding parameters of g and D (for the five-coordinate Co(II) ions), of A, κ, λ, and Δ (for the metals with spin-orbit coupling) and of the exchange constants J. The agreement with results from DFT calculations, also presented here, is remarkable. 相似文献
15.
Unitary group adapted state specific multireference perturbation theory: Formulation and pilot applications
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Avijit Sen Sangita Sen Pradipta Kumar Samanta Debashis Mukherjee 《Journal of computational chemistry》2015,36(9):670-688
We present here a comprehensive account of the formulation and pilot applications of the second‐order perturbative analogue of the recently proposed unitary group adapted state‐specific multireference coupled cluster theory (UGA‐SSMRCC), which we call as the UGA‐SSMRPT2. We also discuss the essential similarities and differences between the UGA‐SSMRPT2 and the allied SA‐SSMRPT2. Our theory, like its parent UGA‐SSMRCC formalism, is size‐extensive. However, because of the noninvariance of the theory with respect to the transformation among the active orbitals, it requires the use of localized orbitals to ensure size‐consistency. We have demonstrated the performance of the formalism with a set of pilot applications, exploring (a) the accuracy of the potential energy surface (PES) of a set of small prototypical difficult molecules in their various low‐lying states, using natural, pseudocanonical and localized orbitals and compared the respective nonparallelity errors (NPE) and the mean average deviations (MAD) vis‐a‐vis the full CI results with the same basis; (b) the efficacy of localized active orbitals to ensure and demonstrate manifest size‐consistency with respect to fragmentation. We found that natural orbitals lead to the best overall PES, as evidenced by the NPE and MAD values. The MRMP2 results for individual states and of the MCQDPT2 for multiple states displaying avoided curve crossings are uniformly poorer as compared with the UGA‐SSMRPT2 results. The striking aspect of the size‐consistency check is the complete insensitivity of the sum of fragment energies with given fragment spin‐multiplicities, which are obtained as the asymptotic limit of super‐molecules with different coupled spins. © 2015 Wiley Periodicals, Inc. 相似文献
16.
17.
In this paper we present a method of incorporating spin-adapted configurations in a Many-Body Perturbation Theory (MBPT) framework. It has been demonstrated how the use of doubly excited Serber-type spinadapted configurations leads in a straightforward way to a well-defined MBPT series which in effect involves an infinite summation of orbital-diagonal ladders for all possible spin allocations. The formalism implicitly defines a partition of the hamiltonian in which the diagonal matrix elements of the hamiltonian in the Serber-type configurations figure as the unperturbed part. This may thus be called a spin-adapted Epstein-Nesbet (E-N) type of partition. The formalism has been tested on a selection of 6π-electron conjugated systems where we have calculated their orbital pair-correlation energies, and compared the performance against E-N perturbation results and a variational calculation of the same quantities. The comparison reveals that, with canonical Hartree-Fock orbitals, the E-N partition tends to overestimate the pair-correction energy which the spinadapted formalism tends to compensate, but without involving much additional effort. The results for the localized H-F orbitals are rather less sensitive and no definitive conclusions could be discerned for them. The advantages of using the spin-adapted MBPT formalism have also been delineated. 相似文献
18.
In this paper certain correspondences have been shown among various formulations of coupled-cluster theories for many electron
closed-shell systems. Specifically it is shown that (i) the energy functional using unitary ansatz of the form exp (T−T
+) is exactly sameorder by order inT with the size-consistent energy functional 〈ψ|H|ψ〉/〈ψ|ψ〉 recently obtained by us in coupled-cluster framework; (ii) in the framework of unitary ansatz of the form exp (T−T
+), both non-variational and variational approaches lead to identical equations upto any given order inT andT
+ inT∼T
2 approximation; (iii) variational procedure using our size-consistent energy functional or using the functional obtained in
the framework of unitary ansatz (as envisaged by Kutzelnigg) leads to energy in both cases, inT∼T
2 approximation, for a total of quadratic powers inT andT
+, same as Cizek’s linearised coupled pair many electron theory energy; (iv) in case of practical calculation of the energy
through the variational procedures using our size-consistent energy functional and the functional in unitary ansatz framework,
there is a loss of upper bound. 相似文献
19.
In this paper we develop a simple method for adapting the closed-shell many-body perturbation theory to an arbitrary point
group symmetry taking account of various classes of diagrams exactly to all orders. The method consists in deriving a linear
operator equation for the closed-shell wave-operatorW which is then symmetry-adapted to the pertinent point groupG. It is shown that the system of equations thus derived enables one to include orbital-diagonalh-h, p-p andh-p ladders to all orders in a perturbative framework. The way to generalise the method through inclusion of a larger classes
of diagrams to all orders is also indicated. Finally, the connection of the present mode of development with the non-perturbative
coupled-cluster formalisms is briefly indicated. 相似文献
20.
Panda D Mishra PP Khatua S Koner AL Sunoj RB Datta A 《The journal of physical chemistry. A》2006,110(17):5585-5591
The photophysics of the fluorescent probe Lucifer yellow CH has been investigated using fluorescence spectroscopic and computational techniques. The nonradiative rate is found to pass through a minimum in solvents of intermediate empirical polarity. This apparently anomalous behavior is rationalized by considering the possibility of predominance of different kinds of nonradiative processes, viz. intersystem crossing (ISC) and excited-state proton transfer (ESPT), in solvents of low and high empirical polarity, respectively. The feasibility of the proton transfer is examined by the structure determined by the density functional theory (DFT) calculations. The predicted energy levels based on the time-dependent density functional theory (TD-DFT) method in the gas phase identifies the energy gap between the S(1) and nearest triplet state to be close enough to facilitate ISC. Photophysical investigation in solvent mixtures and in deuterated solvents clearly indicates the predominance of the solvent-mediated intramolecular proton transfer in the excited state of the fluorophore in protic solvents. 相似文献