光学双稳性临界点的相变行为

本文详细地讨论了光学双稳性(OB)的临界现象。理论分析主要以忽略量子涨落的Fokker-Plank方程的静态解为基础。结果发现,OB的临界现象可以纳入Landau二级相变理论的框架,并且有关临界指数之间的关系也服从标度律。 关键词：     

Tetramethylammonium-calcium-triazid. Darstellung und Kristallstruktur

[N(CH₃)₄]Ca(N₃)₃,M=240.29, was prepared from aqueous solutions of tetramethylammoniumazide with calciumazide at 298 K. The crystals are tetragonala=936.6(7) pm,c=694.7(5)pm, space group P4/nmm,Z=2, (x)=1.31Mgm^–3. The crystal structure was determined by single crystal x-ray diffraction (234 Mo-K-reflections, =0.469 mm^–1,R=0.064). Calcium is octahedrally coordinated to six azide groups. The octahedra are connected via azide groups to a threedimensional array with the complex ammonium ions between. The terminal nitrogen atoms of the azide groups and the methyl groups are considerably disordered.

     

Synthesis and Structural Characterization of [Mn(ethyl isonicotinate)(2)(N(3))(2)](n)(), a Two-Dimensional Alternating Ferromagnetic-Antiferromagnetic Compound. Magnetostructural Correlations for the End-to-End Pseudohalide-Manganese System

Three compounds with formula [Mn(L)(2)(N(3))(2)](n)(), in which L is 4-acpy = 4-acetylpyridine (1), Etinc = ethyl isonicotinate (2), and py = pyridine (3), have been studied from the magnetic point of view. The new compound [Mn(L)(2)(N(3))(2)](n)() (2) crystallizes in the monoclinic system, space group P2(1)/a (No. 14), formula [C(16)H(18)MnN(8)O(4)], with a = 15.176(5) ?, b = 9.060(3) ?, c = 15.760(6) ?, beta = 111.62(3) degrees, and Z = 4. Compounds 1 and 2 are two-dimensional systems, whereas 3 is a 3-D compound. Compound 2 shows ferromagnetic Mn(2)(N(3))(2) dimeric entities linked antiferromagnetically to the four neighboring dimeric entities by four end-to-end azido bridges, leading to an alternate ferromagnetic-antiferromagnetic two-dimensional compound. MO calculations have been performed to study the superexchange pathway for the manganese 1,3-azido system.     

Stepwise hydration and multibody deprotonation with steep negative temperature dependence in the benzene.+ -water system

We studied the stepwise hydration and solvent-mediated deprotonation of the benzene*+ cation (Bz*+) and found several unusual features. The solvent binding energies DeltaH on-1,n for the reactions Bz*+(H2O)n-1 + H2O --> Bz*+(H2O)n are nearly constant at 9 +/- 1 kcal mol-1 for n = 1 to 8. We observed a remarkable sudden decrease in the entropy of association accompanying the formation of Bz*+(H2O)7 and Bz*+(H2O)8, indicating strong orientational restraint in the hydration shells of these clusters consistent with the formation of cagelike structures. We observed the size-dependent deprotonation of Bz*+ in a cooperative multibody process, where n H2O molecules (n >/= 4) can remove a proton from Bz*+ to form protonated water clusters. We measured, for the first time, the temperature dependence of such a process and found a negative temperature coefficient of a magnitude unprecedented in any chemical reaction, of the form k = AT-67+/- 4, or in an Arrhenius form having an activation energy of -34 +/- 1 kcal mol-1. The temperature effect may be explained by Bz*+ and four H2O molecules needing to be assembled from gas-phase components to form the reactive species. Such large temperature effects may be therefore general in solvent cluster-mediated reactions.     

Crystal structure and spectroscopic study of di-μ(1,1)-azido-di-μ(0,0-nitrato)tetrakis(3,5-lutidine)dicopper(II), [Cu(N3) (NO3) (3,5-lutidine)2]2

A mixed ligand 12 complex of copper(II) azide with 3,5-lutidine, namely di-(1,1)-azido-di(0,0)-nitrato)tetrakis(3,5-lutidine)dicopper(II) has been prepared and characterized by X-ray crystallographic and spectroscopic methods. The dimeric molecule, which possesses a crystallographic inversion center, contains two(1,1) bridging azido ligands. Each copper(II) atom in the cyclic Cu₂N₂ unit is further coordinated by two oxygen atoms from two(0,0-nitrato) bridges at Cu-O distances of 2.465(3) and 2.568(3) Å and two nitrogen atoms from the lutidine molecules [Cu-N=2.003(3) and 2.012(3) Å] to give a distorted tetragonal bipyramid. Both azido ligands are linear [N-N-N angle=179.0(4) and asymmetric N-N=1.207(4) and N-N=1.135(5) Å]. The azido bridges produce a rather short Cu Cu distance of 3.013(2) Å. Infrared and electronic data are presented and discussed.     

Synthesis and structure of two lanthanide complexes with isonicotinic acid N-oxide (HL): [Ln(L)2(H2O)4]n·(NO3)n·n(H2O) (Ln = Sm or Tb)

Two new lanthanide complexes of isonicotinic acid N-oxide (HL), namely [Ln(L)₂(H₂O)₄]_n·(NO₃)_n·n(H₂O) for Ln = Sm or Tb, have been synthesized and characterized by spectroscopic and crystallographic methods. IR spectra suggest that isonicotinic acid N-oxide acts as a O,O′-bidentate ligand, the N-oxide group as well as the nitrate group are not involved in coordination. Single crystal analyses have shown that both complexes are isomorphous, where the Ln(III) centers are eight coordinated by four O atoms of four water ligands and other four O atoms of two isonicotinic acid N-oxide ligands. The carboxylate groups are only involved in the bidentate syn–syn bridging mode into infinite chains. Hydrogen bonds between aqua ligands, lattice molecules, nitrate and N-oxide groups are formed giving a three-dimensional network.     

Topological ferrimagnetic behavior of two new [Mn(L)2(N3)2]n chains with the new AF/AF/F alternating sequence (L = 3-methylpyridine or 3,4-dimethylpyridine)

The reaction of manganese(II) and pyridine derivatives such as 3-methylpyridine (3-Mepy) and 3,4-dimethylpyridine (3,4-Dmepy) led to the new one-dimensional systems trans-[Mn(3-Mepy)2(N3)2]n (1) and trans-[Mn(3,4-Dmepy)2(N3)2]n (2). Compound 1 crystallizes in the monoclinic system, space group P2(1)/n, a = 11.201(3) A, b = 14.499(4) A, c = 14.308(4) A, Z = 6, and compound 2 crystallizes in the triclinic system, space group P1, a = 11.502(4) A, b = 14.246(5) A, c = 16.200(8) A, Z = 6. The two compounds show the same general one-dimensional arrangement of double azido bridges between neighboring manganese atoms with the unprecedented -Mn-(mu(1,3)-N3)2-Mn-(mu(1,3)-N3)2-Mn-(mu(1,1)-N3)2-Mn- sequence. Susceptibility and magnetization measurements reveal a ferrimagnetic-like behavior derived from the topology of the chain. A model of the Heisenberg chain, comprising classical spins coupled through alternating exchange interactions J1J1J2... is proposed to describe the magnetic behavior.     

1D and 2D Systems Derived from Polynuclear [ ML(N 3) 2] n ( M?=?Zn(II) or Cd(II) and L is 2-Picoline- N-oxide or 4-Methylpyrimidine)

Four new polynuclear complexes: [Zn(2picNO)(N₃)₂]_n, [Zn(4Mepym)(N₃)₂]_n, [Cd(2picNO)(N₃)₂]_n, and [Cd(4Mepym)(N₃)₂]_n (2picNO=2-picoline-N-oxide and 4Mepym=4-methylpyrimidine) have been synthesized and characterized by single-crystal X-ray diffraction. The structures of the zinc(II) complexes feature five-coordinate zinc atoms, (-1,1) azido bridges, monodentate organic ligands, and 1D chains. The cadmium(II) azide complexes contain distorted octahedral metal atoms linked by alternate di-(-1,1) and di-(-1,3) azido bridges in cis arrangement and these chains are connected by 2picNO bridges giving a honeycomb 2D framework or by 4Mepym bridges forming extended 2D network structure.