1,721,052 research outputs found
Two dicobalt(iii) complexes of triazolate-containing [2+2] Schiff-base macrocycles coordinate thiocyanate ions via the sulfur atom
No full textHighly unusual S-coordination modes are observed for the four axial thiocyanate co-ligands in two structurally characterised dicobalt(III) [2+2] triazolate-based macrocyclic complexes
Spin crossover in iron(II) complexes of 3,5-di(2-pyridyl)-1,2,4-triazoles and 3,5-di(2-pyridyl)-1,2,4-triazolates
No full textThe iron coordination chemistry of 3,5-di(2-pyridyl)-1,2,4-triazoles and 3,5-di(2-pyridyl)-1,2,4-triazolates is reviewed. This includes both mononuclear and dinuclear complexes, and both iron(II) and iron(III) oxidation states. The main focus is on the synthesis, structure and magnetic properties of these complexes
Nano-magnetic materials: spin crossover compounds vs. single molecule magnets vs. single chain magnets
No full textBrief introductions to spin crossover (SCO), single molecule magnetism (SMM) and single chain magnetism (SCM) are provided. Each section is illustrated by selected examples that have contributed significantly to the development of these fields, including recent efforts to produce materials (films, attachment to surfaces etc.). The advantages and disadvantages of each class of magnetically interesting compound are considered, along with the key challenges that remain to be overcome before such compounds can be used commercially as nanocomponents. This invited perspective article is intended to be easily comprehensible to non-specialists in the field
Alkylations ofN4-(4-Pyridyl)-3,5-di(2-pyridyl)-1,2,4-triazole: first observation of room-temperature rearrangement of anN4-substituted triazole to the N1 analogue
No full textAttempts to use alkylation to introduce a positive charge at the nitrogen atom of the 4-pyridyl ring in the bis(bidentate) triazole ligand N-4-(4-pyridyl)-3,5-di(2-pyridy1)-1,2,4-triazole (pydpt) were made to ascertain what effect a strongly electron-withdrawing group would have on the magnetic properties of any subsequent iron(II) complexes. Alkylation of pydpt under relatively mild conditions led in some cases to unexpected rearrangement products. Specifically, when benzyl bromide is used as the alkylating agent, and the reaction is carried out in refluxing acetonitrile, the N-4 substituent moves to the NI position. However, when the same reaction is performed in dichloromethane at room temperature, the rearrangement does not occur and the desired product containing an alkylated N4 substituent is obtained. Heating a pure sample of N-4-Bzpydpt center dot 3r to reflux in MeCN resulted in clean conversion to N-1-Bzpydpt center dot Br. This is consistent with AP-Bzpydpf Br being the kinetic product whereas N-1-Bzpydpt.Br is the thermodynamic product. When methyl iodide is used as the alkylating agent, the N-4 to N-1 rearrangement occurs even at room temperature, and at reflux pydpt is doubly alkylated. The observation of the lowest reported temperatures for an N-4 to N-1 rearrangement is due to this particular rearrangement involving nucleophilic aromatic substitution: a possible mechanism for this transformation is suggested
A structural investigation of anion-triazole interactions: observation of “?-Pockets” and “?-Sandwiches”
No full textEight mononuclear nickel(II) complexes of the ligands 4-amino-3,5-di(2-pyridyl)-1,2,4-triazole (adpt) and 4-pyrrolyl-3,5-di(2-pyridyl)-1,2,4-triazole (pldpt) with the anions ClO(4), BF(4), PF(6) and SbF(6) have been prepared. In all cases the metal/ligand ratio is 1:3, and the complexes are of the form [NiL(3)](A)(2)center dot solvents where L = adpt or pldpt and A = one of the aforementioned anions. Five of these. complexes have been structurally characterized by X-ray crystallography: four of these contain pldpt and strong anion-pi interactions are observed, with two motifs present in all four structures. One of the anions occupies a "pi-pocket" formed by two coordinated triazole rings and one coordinated pyridine ring. The other anion only interacts with one triazole ring, which is involved in the pocket around the first anion, such that the triazole ring is "sandwiched" by two anions. Surprisingly, in all four of these complexes, the two triazole, centroid center dot center dot center dot anion distances in the anion-triazole-anion interactions [2.917(7)-3.005(10) angstrom] are significantly shorter than in any of the other types of triazole-anion interactions [3.164(5)-3.456(9) angstrom]
High and low spin mononuclear and dinuclear iron(II) complexes of 4-amino and 4-pyrrolyl-3,5-di(2-pyridyl)-4H-1,2,4-triazoles
No full textThe first dinuclear iron(II) complexes of any 4-substituted 3,5-di(2-pyridyl)-4H-1,2,4-triazole ligands, [Fe(II)2(adpt)2(H2O)1.5(CH3CN)2.5](BF4)4 and [Fe(II)2(pldpt)2(H2O)2(CH3CN)2](BF4)4, are presented [where adpt is 4-amino-3,5-di(2-pyridyl)-4H-1,2,4-triazole and pldpt is 4-pyrrolyl-3,5-di(2-pyridyl)-4H-1,2,4-triazole]. Both dinuclear complexes feature doubly triazole bridged iron(II) centers that are found to be [high spin-high spin] at all temperatures, 4-300 K, and to exhibit weak antiferromagnetic coupling. In the analogous monometallic complexes, [Fe(II)(Rdpt)2(X)2](n+), the spin state of the iron(II) center was controlled by appropriate selection of the axial ligands X. Specifically, both of the chloride complexes, [Fe(II)(adpt)2(Cl)2] x 2 MeOH and [Fe(II)(pldpt)2(Cl)2] x 2 MeOH x H2O, were found to be high spin whereas the pyridine adduct [Fe(II)(adpt)2(py)2](BF4)2 was low spin. Attempts to prepare [Fe(II)(pldpt)2(py)2](BF4)2 and the dinuclear analogues [Fe(II)2(Rdpt)2(py)4](BF4)4 failed, illustrating the significant challenges faced in attempts to develop control over the nature of the product obtained from reactions of iron(II) and these bis-bidentate ligands
Spin crossover in co-crystallised 2 ? 1 cis?trans [FeII(pldpt)2(NCS)2] occurs only in ? of the iron centres
No full textThe first spin crossover (SCO) active sample of co-crystallised stereoisomers (cis : trans, 2 : 1) is fully high spin (HS) at room temperature but displays temperature mediated SCO in which only a third of the iron(II) centres change spin state
Copper-induced N–N bond cleavage results in an octanuclear expanded-core grid-like complex
No full textReaction of copper(I) acetate and 4-amino-3,5-di(2-pyridyl)-1,2,4-triazole (adpt) in methanol under ambient conditions yields octanuclear [CuII8(dpt)4(OH)4(OAc)8]; OAc = acetate anion, and dpt? = anion of deaminated adpt, 3,5-di(2-pyridyl)-1,2,4-triazolate. However, reaction of copper(II) acetate with dptH gives tetranuclear [CuII4(dpt)2(OH)(OMe)(OAc)4]
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