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Highlights: [•] Ligands 1 and 2 show unique sensitivity to fluoride anions, and produce concentration-dependent colour switching in UV–vis spectra. [•] We demonstrate unusual role of tryptophan in the coordination of fluoride anion (as in ligand 2). [•] Based on this understanding, we have developed a thin-film sensor for fluoride anions, which can be utilised for real-time applications. [•] This work illustrates the chemical consequences of tryptophan-fluoride interactions from anion receptor perspective. [ABSTRACT FROM AUTHOR]

Abstract: The anion coordination properties of bis-tryptophan dicarboxamide ligands 1–3 were investigated using fluorescence and 1H NMR spectroscopy. It was observed that the coordination of acetate anions to these ligands produced emissions at 381nm with gradual enhancement of fluorescence. In comparison, fluoride produced minor enhancement, the addition of chloride, bromide and nitrate anions caused quenching of ligand fluorescence. 1H NMR studies revealed that the ligands coordinated to the acetate anions through the indole and amide NH groups. [Copyright &y& Elsevier]

Abstract: Two tryptophan-based pyridine dicarboxamide ligands have been synthesised and characterised. 1H NMR studies indicated that these ligands are capable of coordinating to bromide anions through amide/indole NH and CH groups. Based on 1H NMR studies, we found that organic bromides selectively bind to with one of the ligands, as evidenced by complexation induced chemical shifts for the indole and amide NH resonances. [Copyright &y& Elsevier]

Abstract: A 1D-coordination polymer [{Mn3(C6H5COO)6(BPNO)2(MeOH)2}(MeOH)2] n (1) having benzoate as the anionic ligand and 4,4′-bipyridyl-N,N′-dioxide (BPNO) as bridging ligand is synthesized by reacting benzoic acid with manganese(II) acetate tetrahydrate followed by reaction with 4,4′-bipyridyl-NN′-dioxide. The bridging bidentate BPNO ligands in this coordination polymer along with the benzoate bridges hold the repeated units. The chain like structure in one dimension by benzoate bridges are connected to each other through the μ3-η2:η1 bridges of BPNO ligands. This coordination polymer can be transformed to a molecular complex [Mn(H2O)6](C6H5COO)2.4BPNO (2). In this complex the BPNO remains outside the coordination sphere but they are hydrogen bonded to water molecules to form self assembled structure. The reaction of 3,5-pyrazoledicarboxylic acid (L1H2) and BPNO with manganese(II) acetate or zinc(II) acetate led to molecular complexes with composition [M2(L1)2(H2O)6].BPNO·xH2O {where M=Mn(II) (3), Zn(II)(4)}. These molecular complexes of BPNO are characterised by X-ray crystallography. The complexes 3–4 are binuclear carboxylate complexes having M2O2 core formed from carboxylate ligands with two metal ions. [Copyright &y& Elsevier]

Abstract: Dicarboxylate coordination polymers (1–5) of Mn(II), Ni(II), Cu(II), Zn(II) and Cd(II), respectively, derived from (7-carboxymethoxy-naphthalen-2-yloxy)-acetic acid (L 1 H 2 ) are synthesized and characterized. Depending on the coordination sites around the metal centers and coordination mode of the ligand, dimensionality of these polymers varies. The dicarboxylates adopt three spatial orientations: in-plane linear coordination, out-of-plane cis coordination and out-of-plane trans coordination mode. Both the cis and trans out-of-plane coordination modes are found to exist only if the ancillary ligand pyridine is coordinated to the metal ion. When the aquoligand coordinates the in-plane linear coordination mode of L 1 predominates. The coordination polymers 4 and 5 show photoluminescence in solution. The dicarboxylate of (5-carboxymethoxy-naphthalen-1-yloxy)-acetic acid (L 2 H 2 ) does not form coordination polymer under ambient conditions, but prefers to remain as uncoordinated anion providing hydrophobic confinement to hexa-aquometal(II) cation. Compound 3 crystallizes in P21 space group and it shows broadband ultra-violet fluorescence centered at 352.9nm on focusing 632.8nm He:Ne laser. [Copyright &y& Elsevier]

The structural aspects of one-dimensional coordination polymer (1) of nickel(II) with 1,3,5-benzene tricarboxylate and a three-dimensional interpenetrating coordination polymer (2) of zinc(II) with 1,4-benzenedicarboxylate ligand are studied by single crystal X-ray diffraction analysis. Coordination polymer ( 1) forms a hydrogen bonded three dimensional network structures. The coordination polymer 1 having a composition [Ni(TMA)(HO)] where (TMA = trimesate anion), crystallizes in monoclinic crystal system with C2 space group and has a/Å, 17.3387(4); b/Å, 12.8748(4); c/Å, 6.5302(2); β/°111.620(2); V/Å, 1355.20(7). The zinc coordination polymer 2 crystal system is orthorhombic, with space group Pbca. It has a/Å, 14.5049(3); b/Å, 17.1616(3); c/Å, 18.1389(4); V/Å, 4515.27(16). The 1,4-benzenedicarboxylate three dimensional coordination polymer of zinc(II) comprises of novel hydroxo bridged tetranuclear zinc(II) secondary building units and has a composition [Zn(CHCO){(CH)SO}(OH)]. Topological analysis of the three dimensional coordination polymer 2 shows that it has a two fold interpenetrating net topology. Graphical Abstract: Tetranuclear Zn(II) carboxylate cluster leading to 3D coordination polymer.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A simple method for synthesis of manganese(II) coordination polymers with different benzoate ligands and pyridine N-oxide having general composition [Mn(RC6H4CO2)2(PyO)]n is presented (where PyO = pyridine N-oxide and R = H, 1a; R = 4-NO2, 1b; R = 4-Cl, 1c; R = 4-OH, 1d; R = 2-NO2, 1e). All these polymers are characterized by X-ray crystallography and other spectroscopic techniques. The coordination polymers have similar structures, but the positions of the manganese atoms differ. For example, 1c is highly symmetric and a mirror plane exists between each manganese site (2/m). In 1d, the manganese centers are related by an inversion center (-1) whereas in 1e the manganese centers are related by C1 rotation (1). Reaction of manganese(II) acetate tetrahydrate with 4-chlorobenzoic acid and PyO upon crystallization from methanol/pyridine gave crystals of coordination polymer 1c along with aqua-bis-pyridine bis-4-chlorobenzoato manganese(II) (2). The structure of 2 also determined by single-crystal X-ray diffraction has a 1-D hydrogen bonded chain structure. Temperature-dependent zero-field cooled and field-cooled magnetization data of 1a-1c measured at 20 Oe and 1000 Oe show field-dependent magnetization spread over a wide temperature range from 5 to 300 K. These coordination polymers show anti-ferromagnetic behavior below 20 K. [ABSTRACT FROM AUTHOR]

Abstract: The structures of two forms of a mixed anionic one-dimensional coordination polymers of lead(II) nitrate derived from benzoate and 2,2’-bipyridyl N-oxide are reported. The X-ray crystal structures show subtle differences in the two binding modes of nitrate in the coordination polymers obtained from two independent solvents. The solid state UV–Vis spectra show differences in the absorption pattern of the crystalline solids obtained from different solvents. The solid state UV–Vis spectra as well as the solution spectra are compared. [Copyright &y& Elsevier]

Abstract: Aqua-bridged binuclear cobalt (II) benzoate complexes having pyridine as auxiliary ligands are synthesised through solid state reactions and characterised. The binuclear core in these complexes comprise of two bridging benzoates and an aqua bridge. Each of the cobalt (II) centre is further co-ordinated to one benzoate and two pyridine ligands. The aqua-bridged cobalt (II) benzoate complex [Co2(μ-H2O)(μ-OBz)2(OBz)2(Py)4]· (C6H6)(BzOH) (1a) is inclusion compounds with benzoic acid and benzene (where OBz = benzoate, py = pyridine). Analogous complex [Co2(μ-H2O)(μ-OBz)2(OBz)2(Py)4]·1.5(C6H6) without benzoic acid included is also prepared by an alternative method and structurally characterised. Analogous aqua-bridged complex derived from p-chlorobenzoic acid in unsolvated form is characterised. The Co–O–Co separation in these complexes is in the range of 3.55–3.64Å with angles Co–O–Co varying from 111.8° to 116.4°. While similar reaction in solution leads to the formation of mononuclear complex having composition [Co(OBz)2(Py)2(H2O)]. The unsubstituted benzoate complex 1a can be easily oxidised to form a tetrameric cobalt (III) complex having benzoate and oxo-bridged structure with a Co4O4 core. [Copyright &y& Elsevier]