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A rational design based on the proton-coupled electron transfer (PCET) concept allows us to structurally characterize for the first time isolable, air- and moisture-stable semiquinone radicals in a zwitterionic neutral form. The presence of an alkoxy and the bulky pyridinio substituents causes only a minor perturbation of either the redox potentials or the spectral UV-vis characteristics of the semiquinone core but significantly stabilizes the new radicals.
We present a series of eight layered copper(II) malonates, each with a {[HA](2)[Cu(II)(mal)(2)(H(2)O)]}(n) A-B-A layer structure, where A is an ammonium cation and 13 is an anionic copper malonate layer (x = 1 or 2; A = benzylamine, 1; S-(alpha)-methylbenzylamine, 2; 4-methylbenzylamine, 3; 4-carboxybenzylamine, 4; 4-trifluoromethylbenzylamine, 5; 4-trifluoromethoxybenzylamine, 6; phenylethylamine, 7; and 4-fluorophenylethylamine, 8). The ammonium cations used are primary amines based around benzylamine and phenylethylamine and include several different functional groups. The different amines give a large array of interlayer interactions, including van der Wail Is packing, hydrogen bonding, C-H center dot center dot center dot pi, pi-center dot center dot center dot pi, H center dot center dot center dot F, and F center dot center dot ...
A π-extended, redox-active tetradentate tetrathiafulvalene-fused salphen [salphen = N,N′-phenylenebis(salicylideneimine)] compound (L) was prepared via a direct Schiff-base condensation of the corresponding diamine-tetrathiafulvalene (TTF) precursor with salicylaldehyde. Its chelating coordination ability has been demonstrated by the formation of the corresponding transition metal complexes in the presence of M(OAc)2·nH2O (M = Co(II), Ni(II), Cu(II)) and FeCl3·6H2O. Three complexes have been characterized by single-crystal X-ray diffraction analysis showing that the TTF-salphen ligand coordinates to the metal ions in a planar mode through the nitrogen and oxygen atoms in a N2O2 cis-configuration. In the case of Fe(III), a dinuclear oxo-bridged Fe(III) complex is formed. These paramagnetic complexes are promising building blocks for the...
Redox-active dithiolated tetrathiafulvalene derivatives (TTFdT) were inserted in two-dimensional nanoparticle arrays to build interlinked networks of molecular junctions. Upon oxidation of the TTFdT to the dication state, we observed a conductance increase of the networks by up to 1 order of magnitude. Successive oxidation and reduction cycles demonstrated a clear switching behavior of the molecular junction conductance. These results show the potential of interlinked nanoparticle arrays as chemical sensors.
High resolution friction force maps of the benzylammonium terminated crystalline surface of a layer compound are presented. The lateral force map acquired with an atomic force microscope, reveals a significant contrast between different molecular orientations yielding molecular rows which differ from their neighboring ones. The single crystals are formed by stacks of copper oxalate sheets sandwiched between stereoregular organic cations, resulting in highly organized surface structures. Single molecular defects are observed at small loads. The experimental results are compared with numerical calculations which indicate a transition from an unperturbed state at small loads to a distorted state at higher loads. (C) 2011 American Institute of Physics.
Different synthetic routes have been used for the preparation of a new tetranuclear [Fe4O2(O2CCMe3)(8)(bpm)] cluster (1) and a one-dimensional coordination polymer [Fe4O2-(O2CCMe3)(8)(hmta)](n) (2) (bpm = 2,2'-bipyrimidine and hmta = hexamethylenetetramine). For cluster 1, two structural isomers, 1a and 1b center dot 3MeCN, have been found. X-ray crystallographic analysis showed that all complexes consist of a central {Fe-4(mu(3)-O)(2)}(8+) core. In 1a, metal ions in the core are additionally linked by six bridging pivalates as two other pivalates and a bpm ligand are chelated to Fe-III ions, whereas in cluster 1b, metal ions in the {Fe-4(mu(3)-O)(2)}(8+) core are linked by seven bridging pivalates and only one carboxylate as well as bpm are chelated to the iron centers. In coordination polymer 2, [Fe4O2(O2CCMe3)(8)] clusters are bridg...
We present a detailed analysis of the magnetic properties of two Cu(II) coordination compounds with the tetrazole-1-acetate ligand (t1a), previously reported in literature by Yu et al. [Q. Yu, X. Zhang, H. Bian, H. Liang, B. Zhao, S. Yan, D. Liao, Cryst. Growth Des. 8 (2008) 1140] and simultaneously synthesised independently by ourselves. We focus on methods of describing the susceptibility and magnetisation of a ferromagnetically-coupled S = 1/2 square network (2) and a tetranuclear S = 1/2 'butterfly' cluster (4) as well as discussion of the energy levels of such a cluster.
We have synthesized a new one-dimensional coordination polymer, [CuII(HL)2(4,4′-bpy)]n·2nH2O (1), (HL– = monodeprotonated 3-nitrophthalic acid, 4,4′-bpy = 4,4′-bipyridine) consisting of infinite chains of [CuII(HL)2(4,4′-bpy)]n and have investigated its structure and magnetic properties. Compound 1 crystallizes in the monoclinic C2/c space group with the [CuII(HL)2(4,4′-bpy)]n chains running parallel to the b axis. The chains are linked together by hydrogen bonding between the HL– groups and water molecules to form the three-dimensional crystal structure. The magnetic susceptibility of 1 can be well described using an antiferromagnetic S = 1/2 chain model with g = 2.11(1) and 2J = –0.61(1) cm–1. Several techniques for describing the susceptibility of S =1/2 chains are examined to compare their validity at lowvalues of kT/|2J|, includin...
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