Search results for "Crystal engineering"
showing 10 items of 68 documents
Crystal Engineering of Multifunctional Molecular Materials
2007
In this paper we will focus on the crystal engineering of molecular materials exhibiting magnetic and/or electrical properties. The complexity of these materials needs of a precise design of the molecular building blocks, a control of the intermolecular interactions (hydrogen bonds, host/guest interactions, etc.) and a mastery in crystallization techni- ques in order to design crystal structures exhibiting useful physical proper- ties. We will illustrate this concept through some relevant examples based on two-component hybrid materials.
ChemInform Abstract: Dimeric Resorcin[4]arene Capsules in the Solid State
2012
Supramolecular chemistry research is focused on the study of weak non-covalent intermolecular — that is, supramolecular — interactions as the driving force in self-assembly and molecular recognition. Dimeric resorcin[4]arenes capsules have been a focus of our research for the last 15 years. This review describes the solid state complexation studies of unsubstituted phenolic resorcin[4]arenes and pyrogall[4]arenes towards the formation of dimeric capsules and assemblies using ionic and neutral species as guest molecules and templates. The multitude of different crystal structures obtained during these studies demonstrates the versatile nature of resorcin[4]arenes and pyrogall[4]arenes (2-hyd…
Dimeric Resorcin[4jarene Capsules in the Solid State
2011
Supramolecular chemistry research is focused on the study of weak non-covalent intermolecular — that is, supramolecular — interactions as the driving force in self-assembly and molecular recognition. Dimeric resorcin[4]arenes capsules have been a focus of our research for the last 15 years. This review describes the solid state complexation studies of unsubstituted phenolic resorcin[4]arenes and pyrogall[4]arenes towards the formation of dimeric capsules and assemblies using ionic and neutral species as guest molecules and templates. The multitude of different crystal structures obtained during these studies demonstrates the versatile nature of resorcin[4]arenes and pyrogall[4]arenes (2-hyd…
Nitroxide Radicals as Templating Agents in the Synthesis of Magnets Based on Three-Dimensional Oxalato-Bridged Heterodimetallic Networks
2001
Restricting Magnetic Interaction Pathways in Polyoxometalate Salts of Cationic Nitronyl Nitroxide Free Radicals
2004
Abstract : Salts 1 and 2 that combine the [W 6 O 19 ] 2- Lindqvist anion with the cationic nitronyl nitroxide (NN) free radicals p -MepyNN + and n Bu 3 NCH 2 NN + , respectively, have been synthesized and their structural and magnetic properties have been studied. Keywords: Nitroxide radicals, polyoxometalates, magnetism. Introduction Ferromagnetism based on purely organic materials has raised a lot of interest during the last decade [1]. Most of the studies have been performed with nitronyl nitroxide (NN) radicals due to their persistence, stability and ease of functionalization [2]. Bulk ferromagnetism in these compounds arises from ferromagnetic interactions between open-shell molecules …
Breathing effect in a cobalt phosphonate upon dehydration/rehydration: a single-crystal-to-single-crystal study.
2013
Two cobalt phosphonates, [Co2(2,2′-bpy)2(H2O)(pbtcH)] (1) and [Co2(H2O)(pbtcH)(phen)2] (2; pbtcH5=5-phosphonatophenyl-1,2,4-tricarboxylic acid, 2,2′-bpy=2,2′-bipyridine, phen=1,10-phenanthroline), with layer structures are reported. Compound 1 contains O-C-O and O-P-O bridged tetramers of Co4, which are further connected by pbtcH(4-) units to form a layer. In compound 2, the cobalt tetramers made up of water-bridged Co2 dimers and O-P-O linkages are connected into a layer by pbtcH(4-) units. Upon dehydration, compounds 1 and 2 experience single-crystal-to-single-crystal (SC-SC) structural transformations to form [Co2(2,2′-bpy)2(pbtcH)] (1 a) and [Co2(pbtcH)(phen)2] (2 a), respectively. The …
Optimal arrangements of 1,3-diphenylisobenzofuran molecule pairs for fast singlet fission.
2019
A simplified version of the frontier orbital model has been applied to pairs of C2, C2v, Cs, and C1 symmetry 1,3-diphenylisobenzofuran rotamers to determine their best packing for fast singlet fission (SF). For each rotamer the square of the electronic matrix element for SF was calculated at 2.2 × 109 pair geometries and a few thousand most significant physically accessible local maxima were identified in the six-dimensional space of mutual arrangements. At these pair geometries, SF energy balance was evaluated, relative SF rate constants were approximated using Marcus theory, and the SF rate constant kSF was maximized by further optimization of the geometry of the molecular pair. The proce…
Crystal engineering of 3-D coordination polymers by pillaring ferromagnetic copper(ii)-methylmalonate layers
2007
Three new copper(II) complexes of formula [Cu(Memal)(H2O)]n (1), [Cu2(pyz)(Memal)2] (2) and [Cu2(4,4′-bpy)(Memal)2(H2O)2] (3) (Memal = methylmalonate, pyz = pyrazine and 4,4′-bpy = 4,4′-bipyridine) were obtained and structurally characterized by X-ray diffraction. Complex 1 is a square grid of aquacopper(II) units which are linked by carboxylate-methylmalonate groups in the anti–syn (equatorial–equatorial) coordination mode. The crystal structures of 2 and 3 consist of corrugated layers of copper(II) (2) and aquacopper(II) (3) units with intralayer carboxylate-methylmalonate bridges in the anti–syn (equatorial–apical) coordination mode which are linked through pyrazine (2) and 4,4′-bipyridi…
C3-symmetric trinuclear copper(ii) species as tectons in crystal engineering
2013
Three new complexes have been obtained using C3-symmetric trinuclear complexes as tectons; [Cu3(felden)(NCS)3(dmf)3] (1), [Cu3(felden)(mand)3]·(C2H5)2O (2), and [Cu3(felden)(dca)3(C2H5OH)]·2H2O (3) (H3felden is the Schiff base resulting from the condensation of 2,4,6-triformylphloroglucinol with N,N-dimethylethylenediamine, mand− is the anion of the R-mandelic acid and dca− is the dicyanamide anion). Compounds 1 and 2 are discrete trinuclear species, while compound 3 is a 2D coordination polymer, constructed from trinuclear nodes and dicyanamido spacers. The variable-temperature magnetic properties of 1–3 have been investigated and they reveal the occurrence of weak antiferromagnetic intera…
A Hydrogen-Bonded Supramolecular meso-Helix
2003
[EN] A new one-dimensional hydrogen-bonded polymer with a unique meso-helical structure has been prepared from the spontaneous self-assembly in the solid-state of meta-substituted phenylene dioxamic acid diethyl ester monomers. The helical nature of this molecule and its self-complementary character, through intermolecular hydrogen bonding between oxamic acid ester functions, are the two main factors responsible for the crystalline aggregation process, as confirmed by both experimental X-ray crystallographic data and theoretical ab initio calculations.