A dodecameric water cluster built around a cyclic quasiplanar hexameric core in an organic supramolecular complex of a cryptand

An infinite network is formed by the hydrogen bonding of a cluster of 12 hydrogen-bonded water molecules (see picture) to the secondary amino nitrogen atoms of a laterally nonsymmetric azacryptand. This mode of association had not previously been predicted or found experimentally

Synthesis, characterization and complexation properties of aheteroditopic cryptand L towards Cu<SUP>II</SUP> and Zn<SUP>II</SUP>: crystal structures of L&#183;3H<SUB>2</SUB>O and[ZnL][ClO<SUB>4</SUB>]<SUB>2</SUB>&#183;2H<SUB>2</SUB>O

A new heteroditopic cryptand (L) has been synthesized in high yields, at 5 &#176;C and in absence of any templating metal ion, by tripod-tripod Schiff-base condensation of tris(3-aminopropyl)amine and 2,2',2''-nitrilotris- (ethyleneoxy)tris(benzaldehyde) followed by reduction in situ with NaBH4. The molecule has an endo-endo conformation with a distance of 5.291 &#197; between the two bridgehead nitrogens. The cryptand forms mononuclear cryptates of the general formula [ML][ClO4]2 with copper(II) and zinc(II) perchlorates. The crystal structure of [ZnL][ClO4]2&#183;2H2O was determined. The ZnII occupies the N4 end of the cavity in an almost ideal tetrahedral geometry. The blue copper(II) cryptate exhibits ligand-field bands at 875 and 745 nm and a ligand-to-metal charge transfer at 275 nm in acetonitrile solution at 298 K indicative of pseudo-tetrahedral CuN4 co-ordination. However, its EPR spectral characteristics in the solid state or in solution are typical of a magnetically concentrated complex

Metal-organic framework structures of Cu(II) with pyridine-2,6-dicarboxylate and different spacers: identification of a metal bound acyclic water tetramer

The ligand pyridine-2,6-dicarboxylic acid (pdcH2) reacts under hydrothermal conditions, with Cu(NO3)2&#183;6H2O in the presence of different N-heterocycles used as spacers to form 1D, 2D or 3D metal-organic framework structures depending on the nature of the spacer. These network structures are characterized by X-ray crystallography, variable temperature magnetic measurements, powder X-ray diffraction, infrared and thermal gravimetric analyses. With 4,4'-bipyridine spacer, a 2D network is formed where every alternate Cu(II) ion in the chain is coordinated terminally to an acyclic tetrameric water cluster

Fluorescence-enhancement with different ionic inputs in a cryptand-based multi-receptor signalling system

Abstract. Two molecules of a laterally non-symmetric aza cryptand have been attached to 9,10-dimethylanthracene to obtain a multi-receptor fluorescent signalling system in the &quot;receptor-spacer-fluorophore-spacer-receptor&quot; format. In the absence of a metal ion, weak fluorescence is observed upon excitation of the anthryl group owing to efficient photo-induced electron transfer (PET) of the lone pair of N attached to the anthryl group. However, when a metal salt is added, the lone pair is engaged, thus in blocking of the PET and leading to recovery of fluorescence to different extents depending upon the nature of the metal ion

Synthesis and characterization of mono- and bis-D-π-A cryptand derivatives for second-order nonlinear optics and its modulation with different metal ion inputs

Two new classes of mono- and bis-D-&#960;-A cryptand derivatives with a flexible and a rigid cryptand core have been synthesized. The linear and nonlinear optical properties of these molecules are probed. The three dimensional cavity of the cryptand moiety has been utilized to modulate the SHG intensity to different extents in solution with metal ion inputs such as NiII, CuII, ZnII, and CdII. We also report that decomplexation events can be used to reversibly modulate their NLO responses

Template synthesis of a macrobicyclic cryptand having mixed donors via [2+3] Schiff base condensation

Tris(2-aminoethyl)amine undergoes [2+3] Schiff base condensation with diisobutyraldehyde disulphide in presence of Cs+ ion as the template. This Schiff base, on subsequent reduction by NaBH4, affords the cryptand (3) in overall 52% yield

The first D-π-A octupolar cryptand molecule to exhibit bulk non-linearity

The cryptand derivative has H-bond mediated trigonal network structure that leads to octupolar bulk nonlinearity

A new class of three dimensional D-π-A trigonal cryptand derivatives for second-order nonlinear optics

Synthesis, crystal structures, linear and nonlinear optical properties of tris D-&#960;-A cryptand derivatives with C3 symmetry are reported. Three fold symmetry inherent in the cryptand molecules has been utilized for designing these molecules. Molecular nonlinearities have been measured by hyper-Rayleigh scattering (HRS) experiments. Among the compounds studied, L1 adopts non-centrosymmetric crystal structure. Compounds L1, L2, L3 and L4 show a measurable SHG powder signal. These molecules are more isotropic and have significantly higher melting points than the classical p-nitroaniline based dipolar NLO compounds, making them useful for further device applications. Besides, different acceptor groups can be attached to the cryptand molecules to modulate their NLO properties

Lewis acid-induced rearrangment of α-[bis(methylthio)methylene]ethyl-2-styrylcyclopropylcarbinols: unexpected formation of a novel bicyclo[3.2.1]octadiene framework

The α-[bis(methylthio)methylene]ethyl-2-styrylcyclopropylcarbinols 9a-c undergo a simple but unexpected skeletal rearrangement in the presence of stannic chloride in nitromethane to afford bicyclo[3.2.1]octadiene derivatives 10a-c exclusively in good yields. The structure of 10a was conclusively elucidated by X-ray diffraction studies. A possible mechanism governing the formation of 10 is proposed

Gas adsorption, magnetism, and single-crystal to single-crystal transformation studies of a three-dimensional Mn(II) porous coordination polymer

A porous coordination polymer {[Mn2(DBIBA)3]×(NO3)·3DMF·4H2O}n (1) [DBIBAH = 3,5-di(1H-benzo[d]imidazol-1-yl)benzoic acid] has been synthesized solvothermally and structurally characterized by single-crystal X-ray diffraction. This compound shows significant selective CO2 uptake at low temperature. 1 exhibits antiferromagnetic properties below 17 K, confirmed by magnetic susceptibility measurements. Four new coordination polymers: {[Mn2(DBIBA)3]·ClO4·3DMF·3H2O}n (2), {[Mn2(DBIBA)3]×Cl×DMF×H2O}n (3), {[Mn2(DBIBA)3]×NO3×CH3OH×7H2O}n (4) and {[Mn2(DBIBA)3]×NO3×2CH3COCH3×H2O}n (5), have been synthesized from 1 via anion/solvent exchange protocols at room temperature