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Two pentacoordinated dinuclear copper(II) compounds of the type [Cu2(bpbd)2(dca)](ClO4/PF6)3 (1/2) [bpbd = N,N′-(bis-(pyridin-2-yl)benzylidene)-1,4-butanediamine; dca = dicyanamide] have been synthesized and characterized on the basis of microanalytical, spectroscopic, thermal and other physicochemical results. Single crystal X-ray diffraction measurements of 1 and 2 have been made to define their coordination spheres as well as intermolecular interactions. Structural analyses reveal that 1 and 2 have two copper(II) centers bound by four N atoms of bpbd and the metal centers are connected by a single μ1,5 dca bridge. Both the copper(II) centers in 1 have distorted trigonal bipyramidal geometry; whereas, in 2 one copper(II) center has a distorted trigonal bipyramidal geometry and the other adopts a distorted square pyramidal environment. In the crystalline state, individual 0D units in 1 and 2 are self-assembled with C—H···π interactions promoting dimensionalities. Both complexes show intraligand 1(π—π*) fluorescence in DMF solutions at room temperature. Variable-temperature (300–2 K) magnetic susceptibility studies reveal that long μ1,5 dca bridges mediate very weak antiferromagnetic interactions. [Copyright &y& Elsevier]

Highlights: [•] We report cost effective luminescent as well as electrochemical chemosensors. [•] The sensors can be made following a simple synthetic route. [•] Shape and size selectivity of chemosensors are modelled for biologically important anions (F−, OAc− and ). [•] The sensing interactions are well explained by convenient spectrophotometric and electrochemical techniques. [•] The receptors have improved binding abilities. [ABSTRACT FROM AUTHOR]

Highlights: [•] Three lead (II) terephthalate compounds with two different tetradentate Schiff bases are isolated. [•] X-ray structures reveal hemidirected six-coordinated environment around each lead(II). [•] Thermal studies show different thermal decomposition patterns of the compounds. [•] Compounds exhibit π→π* fluorescence along with ligand-to-metal charge transfer in solid states at room temperature. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two dinuclear cadmium(II) dicarboxylate compounds with polyamine/Schiff base are isolated and characterized. [•] X-ray structures show interesting variations in coordination numbers, geometries and superstructures. [•] Thermogravimetric analyses reveal their thermal stability and decomposition pattern. [•] Fluorescence studies in DMF solution illustrate ligand based π–π* emission. [ABSTRACT FROM AUTHOR]

Abstract: A series of pentacoordinated mono-/dinuclear compounds, [Zn(L)(Br)]PF6 (1), [Zn(L)(NCS)]ClO4 (2) and [Zn2(L)2(μ-tp)](ClO4/PF6)2 (3/4) [L=N,N′-(bis(pyridin-2-yl)benzylidene)-1,3-propanediamine, tp=terephthalate dianion], have been synthesized using one-pot reactions of the building components. All the complexes are characterized using microanalytical, spectroscopic and other physicochemical results. Structures of 1–4 are solved by single crystal X-ray diffraction measurements. Structural analyses reveal that each zinc(II) center in 1 and 3 adopts a distorted trigonal bipyramidal geometry with ZnN4Br and ZnN4O chromophores, respectively, whereas zinc(II) centers in 2 and 4 have a distorted square pyramidal geometry with ZnN5 and ZnN4O chromophores, respectively. Intermolecular CBr, CF and CO hydrogen bondings along with Cπ and π⋯π interactions as the case in 1–4 lead to different crystalline aggregates. The compounds show intraligand π–π* fluorescence in solid states and in DMF solutions at room temperature. [Copyright &y& Elsevier]

Abstract: A 1D coordination polymer [Hg2(L)Br4] n (1) and one dinuclear compound [Hg2(L)I4] (2) [L=N,N′-(bis(pyridin-2-yl)benzylidene)ethane-1,2-diamine] are isolated using a 2:1M ratio of HgBr2/HgI2 and Schiff base (L) in methanol–acetonitrile solution mixture and X-ray crystallographically characterized. Structural analyses show that in 1 1D chain is formed through binucleating bis(bidentate) bridging behavior of L and asymmetric Hg-(μ-Br)2-Hg bridges in an alternate fashion; one terminal bromide unit completes the distorted square pyramidal geometry around each mercury(II). In 2, two mercury(II) centers are connected by bis(bidentate) bridging behavior of L and two iodides bound to each metal(II) center remain as terminal resulting in a discrete dinuclear entity with distorted tetrahedral geometry. Weak intermolecular Hg⋯I and I⋯I interactions in 2 promote dimensionality. In DMF solutions, 1 and 2 display intraligand 1(π–π∗) fluorescence. [Copyright &y& Elsevier]

Abstract: One pentacoordinated mononuclear complex [Zn(L)(NCS)]PF6 (1), one hexacoordinated 2D coordination polymer {[Cd2(L)(NCS)4]·0.24(CH3OH)} n (2) and one pentacoordinated 1D polymeric chain [Hg2(L)(SCN)4] n (3) [L=N,N′-(bis(pyridine-2-yl)benzylidene)-1,4-butanediamine] have been synthesized and X-ray crystallographically characterized. Structural analyses revealed interesting variations in the coordination behaviour of the Schiff base (L) from tetradentate chelation to binucleating bis(bidentate) congregation on going from 1 to 2/3. The pseudohalide exhibits terminal N-coordination in 1, both μ1,3 and μ1,1 bridges in 2 and terminal S-coordination along with μ1,1 linkages in 3. In 1/3, each pentacoordinated zinc(II)/mercury(II) centre adopts a distorted trigonal bipyramidal/square pyramidal geometry with a ZnN5/HgN2S3 chromophore, whereas both Cd1 and Cd2 centres in 2 adopt a distorted octahedral geometry with CdN3S3 and CdN6 chromophores, respectively. Weak intermolecular S···S and S···π interactions with multiple C–H···N hydrogen bonds promote the dimensionalities in 1–3. The complexes display intraligand 1(π–π∗) fluorescence in the solid state and in DMF solutions at room temperature. [Copyright &y& Elsevier]

Abstract: A new end-to-end thiocyanato bridged coordination polymer [Pb(enbzpy)(μ1,3-NCS)(NCS)]n (1) has been synthesized using a one-pot reaction of Pb(OAc)2.3H2O, tetradentate Schiff base N,N΄-(bis(pyridine-2-yl)benzylidene)ethane-1,2-diamine (enbzpy) and NH4NCS in MeOH solution at room temperature. Single crystal X-ray diffraction measurement reveals that each lead(II) adopts a pentagonal bipyramidal geometry with a PbN6S chromophore coordinated through four N atoms of enbzpy, two μ1,3-bridged N and S atoms and one terminal N atom of thiocyanates. In crystalline state, 1 forms a 2D honeycomb like (63) topology through S∙∙∙S interaction and the layers stack through face-to-face π∙∙∙π interaction giving rise to a 3D network. At room temperature DMF solution of 1 displays a high-energy intraligand 1(π-π*) fluorescence. [Copyright &y& Elsevier]

Five hexacoordinated compounds of type [Cd(L)(X)]Y·nMeCN (1–5) [L = N,N′-(bis(pyridin-2-yl)benzylidene)diethylenetriamine; Y = PF6−, n = 1; X = Cl− (1), Br− (2), I− (3) and Y = PF6−, n = 0, X = N3−, (4); Y = ClO4−, n = 0, X = NCO−, (5)] are synthesized and characterized. Structures of all the compounds are solved by X-ray diffraction measurements. Structural analyses reveal that each cadmium(II) center adopts a distorted octahedral geometry bound by five N atoms of L along with terminal halide in 1–3 and N atom of terminal pseudohalide in 4 and 5. Intermolecular N—H···O, C—H···O, N—H···F and C—H···F hydrogen bondings and C—H···π interactions as is the case lead to different crystalline aggregates in 1–5. The complexes display intraligand 1(π—π*) fluorescence in DMF solutions at room temperature. [Copyright &y& Elsevier]

Abstract: Two dinuclear cadmium(II) compounds of the types [Cd(L)(μ-Cl)]2(PF6)2 (1) and [Cd(L)(μ1,5-dca)]2(ClO4)2.0.66MeOH (2) [L=N,N′-(bis(pyridin-2-yl)benzylidene)-1,3-propanediamine; dca=dicyanamide] have been synthesized and characterized on the basis of microanalytical, spectroscopic and other physicochemical results. X-ray structural studies show that in 1 and 2 each hexacoordinated cadmium(II) adopts a distorted octahedral geometry with CdN4Cl2 (1)/CdN6 (2) chromophore ligated through four N atoms of L along with two chlorides in 1 forming a four-membered Cd–(Cl)2–Cd rhombohedral bridging loop and two nitrile N atoms of two μ1,5 dicyanamides in 2 affording a larger 12-membered Cd–(NCNCN)2–Cd ring with boat conformation. In the crystalline state, individual units in 1 are packed through multiple weak CF hydrogen bonds and Cπ and π ⋯π interactions affording a 2D sheet structure. The dinuclear units in 2 are engaged in weak intermolecular CO and CN hydrogen bondings to give a 2D continuum, which is further stabilized by π⋯π interactions through pyridine rings of L. In DMF solutions, 1 and 2 show high-energy intraligand 1(π–π *) fluorescence at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: A tetracoordinated [Hg2(L1)(SCN)4] (1) [L1 =N,N′-(bis-(pyridin-2-yl)benzylidene)-1,2-ethanediamine] and two pentacoordinated [Hg2(L2)(X)4] [L2 =N-((1-pyridin-2-yl)formylidene)-N′-[2-(4-{2-[((1-pyridin-2-yl)formylidene) amino]ethyl}piperazin-1-yl)ethyl]amine; X= , (2) and X=NCS−, (3)] dinuclear mercury(II) compounds have been prepared and characterized using microanalytical, spectroscopic, thermal and X-ray crystallographic results. Structural analyses reveal bis(bidentate) congregation behaviour of classical tetradentate L1 and bis(tridentate) character of L2 encapsulating two metal centers. Each mercury(II) center in 1 is in a distorted tetrahedral coordination environment with HgN2S2 chromophore. Hg(1) is attached with two N atoms of L1 and two S atoms of two terminal thiocyanates whereas neighbouring Hg(1) is ligated to the other two N donor set of the same Schiff base completing its bis(bidentate) mode and two S atoms of thiocyanates. In 2 and 3 each mercury(II) center adopts a distorted square pyramidal geometry with MN5 (in 2) and MN3S2 (in 3) chromophores and two metal(II) centers are encapsulated by bis(tridentate) congregation behaviour of L2 through donation of three N donor set to each metal and the fourth and fifth positions are occupied by two N atoms of terminal azides in 2 and two S atoms of terminal thiocyanates in 3. In solid-state, dinuclear units of 1 pack through cooperative C–H⋯N and C–H⋯S hydrogen bonds and C–H⋯π interactions giving rise to a 3D network. Individual dinuclear units of 2 and 3 self-assemble through cooperative C–H⋯N hydrogen bondings and C–H⋯π interactions affording 3D network structure and 2D continuum, respectively. In DMF solutions at room temperature all the complexes display high-energy intraligand 1(π–π∗) fluorescence. [Copyright &y& Elsevier]

Abstract: Two pentacoordinated dinuclear lead(II) compounds [Pb2(pbap)(N3)4] (1) and [Pb2(pbap)(NCS)4] (2) [pbap= N-((1-pyridin-2-yl)benzylidene)-N′-[2-(4-{2-[((1-pyridin-2-yl)benylidene)amino]ethyl}piperazin-1-yl)ethyl]amine] are prepared and characterized using microanalytical, spectroscopic, thermal and other physicochemical results. Single crystal X-ray diffraction measurements have been made to define the metal coordination spheres. Structural analyses reveal dinucleating bis(tridentate) behaviour of the hexadentate Schiff base (pbap) binding two metal ions. In the centrosymmetric dimers 1 and 2, each lead(II) center adopts a distorted square pyramidal geometry with PbN5 chromophore ligated by each (Np, Ni, Na) donor set of pbap and two N atoms of terminal pseudohalides. In DMF solutions at room temperature the complexes display high-energy intraligand 1(π–π∗) fluorescence. [Copyright &y& Elsevier]

Abstract: Three dinuclear compounds [Cd2(bpbd)3](Y)4 (Y= , 1; , 2) and [Cd(bpbd)(Cl)]2(PF6)2 (3) [bpbd=N,N′-(bis(pyridine-2-yl)benzylidene)-1,4-butanediamine] are prepared and characterized. Structures of 1 and 3 are solved by X-ray study that reveals interesting variation in ligational motifs of bpbd from classical tetradentate chelation binding a single metal ion to bis(bidentate) congregation encapsulating two cadmium(II) centers. In the crystalline state, the dinuclear units of 1 pack through cooperative face-to-face π⋯π interactions and C–H⋯O hydrogen bonds whereas those of 3 are engaged in edge-to-face C–H⋯π interactions and C–H⋯F and C–H⋯Cl hydrogen bonds each leading to 2D sheet structure. High-energy intraligand 1(π–π∗) fluorescence at room temperature in DMF solutions and intraligand 3(π–π∗) phosphorescence in glassy solutions (DMF at 77K) are seen in all the complexes. [Copyright &y& Elsevier]

Abstract: Two heptacoordinated one-dimensional coordination polymers of the type [Cd(L)(dca)] n (X) n (1 and 2) [L= N,N′-(bis-(pyridin-2-yl)benzylidene)diethylenetriamine; dca=dicyanamide; X= (1), (2)] have been prepared and characterized on the basis of microanalytical, spectroscopic and other physicochemical properties. Structures of 1 and 2 are solved by single crystal X-ray diffraction measurements. Structural study reveals that in both compounds each cadmium(II) center adopts a distorted pentagonal bipyramidal geometry with a CdN7 chromophore coordinated by five N atoms of the pentadentate Schiff base and two nitrile N atoms of single bridged dca in μ1,5 fashion. The polynuclear units in 1 are engaged in weak N–H…O and C–H…O hydrogen bondings with perchlorate ions embedded among the chains to give a 2D sheet structure. In the long-range form, the 1D polymeric chains of 2 pack through N–H…F and C–H…F hydrogen bonds with hexafluorophosphate placed in between chains resulting a 2D continuum. The complexes display intraligand 1(π–π∗) fluorescence in DMF solutions at room temperature. [Copyright &y& Elsevier]