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Summary. A formalism has been developed that describes spin crossover equilibrium in the solid state by taking into account the effects
of n nearest neighbours of a given molecule on its partition function. In this way binary and many-body interactions of the order
n + 1 are included into the theoretical model and represented by non-ideality parameters connected with the splitting of free
energy levels. Binary interactions are characterised by the main splittings whereas higher order interactions manifest themselves
in asymmetries of splittings within multiplets. The contribution of molecular interactions can also be written in terms of
formal excess free energies of the second, third, fourth and higher orders. Simple relationships between excess free energies
and parameters of multiplets have been found for binary, ternary and quaternary interactions. This formalism is reduced to
that of the model of binary interactions when effects of surroundings are additive leading to equidistant free energy multiplets.
Higher order interactions may cause an abrupt spin crossover but in a limited range of compositions around the transition
point. The regression of experimental transition curves of one-step spin crossover may yield estimates of excess energies
up to the fifth order. 相似文献
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N. T. Madhu P. K. Radhakrishnan W. Linert 《Journal of Thermal Analysis and Calorimetry》2006,84(3):607-611
The
phenomenological, kinetic and mechanistic aspects of the nitrate, chloride,
bromide and iodide complexes of nickel(II) with1,2-(diimino-4’-antipyrinyl)ethane
(GA) have been studied by TG and DTG techniques. The kinetic parameters like
activation energy, pre-exponential factor and entropy of activation were computed.
The rate controlling process in all stages of decomposition is random nucleation
with one nucleus on each particle (Mampel model). 相似文献
6.
M. Enamullah W. Linert V. Gutmann R. F. Jameson 《Monatshefte für Chemie / Chemical Monthly》1994,125(12):1301-1309
Summary 2,6-bis-(Benzimidazol-2-yl)-pyridine (bzimpy = H2
L) acts as a bidentate ligand when combining with transition metal ions. The complexes [M(bzimpy)2](ClO4)2 (M = Fe2+, Mn2+, Zn2+, Co2+, and Ni2+) were obtained as solids. The protonation constants (logK) for the ligand and the complexes were evaluated in 30:70 (v/v) H2O:EtOH at 293 K and at constant ionic strength of 0.12M KCl. Coordination of the ligand to the metal ions leads to an increase of acidity of the imino-hydrogen of the benzimidazole group of the ligand as a function of the complex stability. Deprotonation leads to a spin-state transition (intermediate spin-state low-spin) of the iron(II)-complex, followed by a shift of the metal-to-ligandcharge transfer band (MLCT) to lower energies (max=563 to 580 nm). The d-d absorption bands are found to shift to higher energies and the low-spin isomer is favoured at room temperature. An opposite shift of theMLCT band (max=563 to 557 nm) is observed when HClO4 is added to the complex solution, rendering the high-spin state of the complex more favourable.On leave from the Chemistry Department, Jahangirnagar University, Dhaka, Bangladesh 相似文献
7.
Chiral resolution of arginine (Arg) and Arg derivatives is demonstrated using electrospray ionization-tandem mass spectrometry (ESI-MS). Calcium ion (Ca(II))-mediated trimeric clusters are generated, which incorporate the analyte of interest and an enantiomerically pure reference molecule of similar metal ion affinity. Two methods, one based on the measurement of a competitive-dissociation-based branching ratio (R(chir)) by the kinetic method (KM) and one based on the measurement of a chiral recognition ratio (CR) by a similar method, are compared. Incorporating N-blocked Arg derivatives (Z-Arg and Boc-Arg) as chiral references provides chiral resolution greater than that previously reported for Arg enantiomers. In a reciprocal manner, pure Arg enantiomers can be used as references for discriminating enantiomers of these N-blocked Arg derivatives. Condensed-phase and gas-phase Ca(II) ion affinity relative to Arg is also addressed qualitatively for other acidic, basic, and neutral amino acids. In some cases, when only one offspring ion is observed (insufficient for KM analysis), the CR method can be applied as an alternative to obtain a measurable stereoselectivity value for the system. The results of these experiments demonstrate the applicability of, and the difference between, the KM and the CR method for improved quantitative analysis of enantiomeric excess for Arg. 相似文献
8.
Svitlana R. Petrusenko Wolfgang Linert Viktoria V. Dyakonenko Oksana V. Nesterova Oleg V. Shishkin 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(7):m281-m283
The title salt, [Zn(C2N2H8)3]2[CdI4]I2, conventionally abbreviated [Zn(en)3]2[CdI4]I2, where en is ethylenediamine, contains discrete [Zn(en)3]2+ cations and [CdI4]2− anions with distorted octahedral and nearly tetrahedral geometries, respectively, as well as uncoordinated I− ions. The cation and the free I− anion lie on twofold rotation axes and the [CdI4]2− anion lies on a axis in the space group I2d. The structure exhibits numerous weak inter‐ionic hydrogen bonds of two types, viz. N—H⋯I−(free ion) and N—H⋯I([CdI4]2−), which support the resulting three‐dimensional framework. 相似文献
9.
Ali Taha Viktor Gutmann Wolfgang Linert 《Monatshefte für Chemie / Chemical Monthly》1991,122(5):327-339
Summary The solvatochromic and thermochromic behaviour of a series of mixed Ni(II) complexes with unsubstituted and substituted -diketones and diamines in the solvents 1,2-dichloroethane (DCE), acetonitrile (An), acetone (AC),n-butanol (n-BuOH), formamide (FA), N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO) and pyridine (PY) has been studied and characterized on the basis of electronic spectra. Spectrophotometric methods have been used to evaluate equilibrium constants and their enthalpic and entropic terms for the formation of Ni(-dik)(diam)L
+ and Ni(-dik)(diam)L
2
+
. Increasing donor strength of the donor-solvents (L) and (or) increasing electronwithdrawing parameters of the substituents at the -diketone and the diamine ligands lead to increasing formation constants, paralleled by relative increase in the stability of the five-coordinated species Ni(-dik)(diam)L
+. The results are discussed in terms of the extended donor-acceptor concept.On leave of absence from the Faculty of Education, Ain Schams University, Roxy, Cairo, Egypt 相似文献
10.