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This paper designed and synthesised a series of V-shaped liquid crystal molecules (X-SBAnE) with resorcinol as the core and Schiff base as the mesogenic arms (X-SBAAn). The effects of polarity of terminal groups (X=-CH3O,-CH3,-Cl) and length of flexible chain (n = 4,6,8) on mesogenic ranges were discussed. The chemical structure of X-SBAAn and X-SBAnE was studied using FT-IR and 1H-NMR while their thermal behaviour and mesogenic ranges were investigated via differential scanning calorimetry (DSC) and polarising optical microscopy (POM). The results indicated that X-SBAAn containing OCH3 and Cl substituents exhibited mesophase except for the analogue having CH3 substituent which was found to be non-mesogenic. All of the synthesised X-SBAnE had liquid crystal properties and exhibited nematic phases in heating and cooling. The length of the flexible spacers and terminal groups significantly influenced their mesogenic ranges. [ABSTRACT FROM AUTHOR]

Two series of novel four-arm azobenzene liquid crystal molecules were designed and synthesized, and their mesophase properties, photo-induced transition were studied. Two series of mesogenic arms were screened with different length of flexible chain (the carbon number n of flexible chain is 4, 6, 8, 10) using methoxy and nitro as terminal substituents R. The four-arm azobenzene LCs were synthesized by introducing the mesogenic arms into cholic acid. FACAE-O-n, FACAE-N-n all belonged to photosensitive thermotropic enantiotropicnematic LCs. For methoxyl series, melting transitions (Tm), liquid crystal-isotropic transitions (Ti) and mesogenic ranges decreased with the increase of carbon numbers in flexible chain both on heating and cooling. The mesophase performance of FACAE-O-4 was the most excellent. For nitro series, Tm and Ti on heating and cooling decreased with the increase of carbon numbers. Nevertheless, mesogenic ranges increased with the increase of carbon numbers only on heating. The cooling mesogenic ranges showed a trend of rising firstly and then falling, reaching the maximum 103.1oC (n=8). Under ultraviolet irradiation, there was no red shift. The intensity of maximum absorption has changed with the increase of ultraviolet irradiation time. After photo-induced, Tm and Ti on heating and cooling of the four-arm LCs decreased, and the mesogenic ranges became shorter. [ABSTRACT FROM AUTHOR]

Twenty novel azobenzene liquid crystal micromolecular compounds named ω-[4-(p-substituted azobenzeneoxy carbonyl]acid (X-ABCnA) have been designed and synthesised, followed by studies on the thermal performance and mesomorphic properties of the compounds. The liquid crystal compounds were divided into five homologous series based on the terminal substituents R (R = CH3O, CH3, H, Cl, NO2). In each series, the number of carbons on flexible chain was 4, 6, 8 and 10, respectively. Fourier-transform infrared, proton nuclear magnetic resonance and elementary analysis demonstrated that the structure of the synthesised azobenzene liquid crystal compounds was consistent with the molecular design. The mesomorphic properties were tested, analysed and characterised by using differential scanning calorimetry and polarised optical microscopy. The melting transition (Tm) of all the compounds in homologous series with different substituents appeared to decrease with the increase of carbon numbers on flexible chains. The same held true for the temperature of isotropic-mesophase/crystalline transition. The compounds with stronger polarity of terminal substituents were more likely to form broader mesogenic ranges. The liquid crystal compounds discussed in this work can be regarded as a reference for the synthesis of mesogenic arms participating in the synthesis of novel multi-arm liquid crystalline macromolecules and polymers. [ABSTRACT FROM AUTHOR]

With cholic acid as the core, five multi-arm ester liquid crystals were synthesised with different terminal substituents. B1–B5 were mesogenic arms which were linked to multifunctional chiral core cholic acid. The effect of electron-withdrawing and electron-donating groups on the mesogenic behaviour of the compounds was discussed. All products were structurally well characterised by elemental analysis, 1HNMR, and FT-IR. The phase behaviours were investigated by means of polarised optical microscopy and differential scanning calorimetry. B2, B4, B5 and C2, C4, C5 and D2, D4, D5 exhibited typical nematic texture and belonged to thermotropic enantiotropic nematic liquid crystals. B3, C3 and D3 also displayed typical nematic texture of thermotropic monotropic nematic liquid crystal. B1, C1 and D1 did not have mesogenic performance. Wider mesogenic range for 81.6°C of C5 whose terminal substituent is nitro on heating cycle while 121.1°C on cooling cycle. The results indicated that terminal substituents have a pretty important effect on the mesogenic phase and range of multi-arm liquid crystal compounds. The mesomorphic behaviour of compounds with polar groups terminally substituted performance much better than those without polar groups. In this ester multi-arm liquid crystal system, electron-withdrawing groups terminally substituted behave better than those electron-donating groups substituted. [ABSTRACT FROM AUTHOR]

A new series of multi-arm liquid crystals (D1-D5) based on cholic acid as the chiral core and ω-[4-(p-substituted azobenzeneoxy carbonyl]valeric acid (B1-B5) as the mesogenic arms were designed and synthesised. All the mesogenic arms and the multi-arm liquid crystals were structurally well-characterised using elementary analysis (EA), 1H NMR and FT-IR. The photochemical properties were determined by UV spectra. The optical rotations were measured by Automatic Polarimeter. The phase behaviours were investigated by means of polarised optical microscopy, X-ray diffraction and differential scanning calorimetry, while the effect of the terminal groups of azobenzene on mesogenic and photochemical properties were discussed. The results demonstrated that the mesogenic arms exhibited nematic phase except B3. The multi-arm compounds showed chiral nematic except D3. Cholic acid played an important role in inducing chiral nematic of the multi-arm liquid crystals. Tm or Ti of B1-B5 and D1-D5 are influenced by the effect of electrical effects of the terminal groups and the molecular shapes. Furthermore, the multi-arm compounds exhibited well light sensitivity, owning the photoisomerisation of the tran-form azobenzene to the cis-form azobenzene. λmax of D1-D5 displayed blue shift first and then red shift with the different electrical effects of the terminal groups of mesogenic arms. [ABSTRACT FROM AUTHOR]

Three new complexes {[Cu( L1)2(NO3)2]⋅H2O}oo ( 1), {[Cu4( L2)2(OAc)8]-CH3CH2OH}oo ( 2) and [Cd2( L3)3(NO3)4(H2O)2]oo ( 3) ( L1=4-phenyl-7-(pyridine-3-yl)-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole, L2=4-(pyridine-3-yl)-7-phenyl-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole, and L3=4-(pyridine-4-yl)-7-phenyl-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole) have been synthesized and characterized by elemental analyses, IR spectra and single crystal X-ray diffraction. The structural analyses reveal that complex 1 is a neutral 2-D network structure with a 44 topology, 2 has a 1-D neutral coordination chain with a [Cu2(CH3COO)4] dinuclear structural unit bridged by four acetate ions, and 3 is a neutral rhombohedral grid structure. All the complexes are air stable at room temperature. Furthermore, the fluorescent properties of complex 3 and corresponding ligand L3 have been investigated and discussed. [ABSTRACT FROM AUTHOR]

Abstract: Two bis(tetrazole) ligands, 1,2-bis(tetrazol-5-ylmethyl)benzene (H2 L1 ) and 1,2-bis(tetrazol-5-yl)benzene (H2 L2 ), were designed and synthesized, and three new zinc(II) and cadmium(II) coordination polymers, {[Zn2(L1 )2(H2O)2]2·8H2O}∞ (1), [Zn4(L1 )4]∞ (2) and {[Cd(L2 )(NH3)3]·2H2O}∞ (3), were synthesized using the ligands H2 L1 and H2 L2 as building blocks. All the complexes were structurally characterized by elemental analyses, IR spectroscopy and X-ray diffraction. Complexes 1 and 3 have infinite one-dimensional (1-D) chain structures, and such 1-D chains structures were linked by complicated hydrogen bonds to form three-dimensional (3-D) supermolecular networks. Complex 2 has a 3-D network structure. In these complexes, the ligands H2 L1 and H2 L2 can act as multidentate ligands when coordinating to the metal ions under different conditions, and three coordination modes for the tetrazolate rings have been observed in these complexes. The results show that the variation of the ligand spacers as well as the reaction conditions lead to the formation of complexes with different structures. Furthermore, the fluorescent properties of complexes 1–3 and ligands H2 L1 and H2 L2 have been investigated and discussed. [Copyright &y& Elsevier]

Abstract: Five new Ag(Ι) metal–organic coordination complexes with dinuclear structure units, Ag2(L1 )2(NO3)2 (1), Ag2(L2 )3(ClO4)2 (2), Ag2(L2 )3(NO3)2 (3), [Ag2(L3 )3(BF4)2](H2O)0.25 (4) and [Ag2(L4 )2(CH3OH)2](ClO4)2 (5) were synthesized, using ligands L1 (N-1,3,4-thiadiazol-2-yl-propionamide), L2 [N-(5-methyl-1,3,4-thiadiazol-2-yl)-propionamide], L3 (N-1,3,4-thiadiazol-2-yl-benzamide) and L4 [N-(5-methyl-1,3,4-thiadiazol-2-yl)-benzamide] as building blocks. All complexes were structurally characterized by elemental analyses, IR spectroscopy and X-ray diffraction. Complexes 1–5 have dinuclear structure units. Compounds 1 and 5 are centrosymmetric different from 2 to 4, in 2–4 two distinct Ag(Ι) were observed in the independent crystallographic dinuclear unit. In 1, 4 and 5, ligands bridge two Ag(Ι) atoms to form an approximately planar binuclear structure containing six-membered ring (Ag–N–N–)2. In complexes 1–5, the Ag⋯Ag weak interactions were observed between the two non-bonding Ag(Ι) centers in the dinuclear unit and the Ag⋯Ag distance are in 3.150–3.481Å. [Copyright &y& Elsevier]

Five new Cu(II)/Mn(II) complexes Cu 2 (H L 1 ) 2 (H 2 O) 2 ( 1 ), [Mn 2 (H L 1 ) 2 (H 2 O) 4 ]·2H 2 O ( 2 ), {[Cu 5 (H L 2 ) 2 (SO 4 ) 2 (OH) 2 (H 2 O) 2 ]·5H 2 O} n ( 3 ), [Cu(H L 2 )] n ( 4 ), Cu 3 ( L 3 ) 2 (OH) 2 (H 2 O) 2 ( 5 ) based on three flexible ligands [bis-(1 H -tetrazol-5-ylmethyl)-amine (H 3 L 1 ), bis-(1 H -tetrazol-5-ylethyl)-amine (H 3 L 2 ) and 1,5-bis(5-tetrazolo)-3-thiapentane (H 2 L 3 )] have been synthesized and structurally characterized, which are in the wide range of 0-D to infinite 2-D network. The dinuclear complexes 1 and 2 can be further assembled into 3-D supramolecular frameworks via hydrogen-bonding interactions, respectively, resulting in a topological pcu and bcu-x net with the Schlafli symbol {4 12 ·6 3 } and {3 36 ·4 48 ·5 7 }. Complexes 3 and 4 feature an infinite 1-D chain and 2-D network, respectively. Both the 2-D framework of 4 and 2-D supramolecular network of 5 can be simplified into a four-connected {4 4 ·6 2 } topological sql network. In addition, the magnetism studies indicate antiferromagnetically coupled systems exist in 1 – 5 . [ABSTRACT FROM AUTHOR]

• Metal-organic frameworks based on imidazole carboxylic acid ligands were synthesized. • MOFs 1 – 3 have antiferromagnetic behavior. • MOF 4 has high selectivity and sensitivity for the detection of Cu2+ and Fe3+. Four new metal-organic frameworks (MOFs), namely [M(H L)H 2 O] n (1–3) [M = Co (1), Ni (2), Cu (3)] and [Cd(H L)] n (4), were successfully structured based on imidazole carboxylic acid ligands [H 3 L = 5-(((1 H -imidazol-2-yl)methyl)amino) isophthalic acid]. X-ray single-crystal diffraction analysis showed that MOFs 1–3 possess the same two-dimensional (2D) planar structure, while MOF 4 exhibited a three-dimensional (3D) coordination network. The magnetic test results showed that MOFs 1–3 have typically antiferromagnetic behavior. The sensing experimental showed that MOF 4 could be considered as a promising bifunctional fluorescent sensor for Cu2+ and Fe3+ ions with excellent selectivity and sensitivity, and the detection limit were 4.11 μM and 4.89 μM, with K sv values of 1.37 × 104 M−1 and 1.24 × 104 M−1, respectively. The cycling experiment illustrated the good reusability of the material. In addition, the fluorescence quenching mechanism of MOF 4 was further explored in detail. Four metal-organic frameworks (MOFs) were constructed based on imidazole carboxylic acid ligands by solvothermal reaction conditions. The MOFs 1–3 have antiferromagnetic behavior. Additionally, MOF 4 has excellent luminescence properties, showing efficient recognition performance, anti-interference performance and recycling performance for Cu2+ and Fe3+. [Display omitted] [ABSTRACT FROM AUTHOR]