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Reaction of copper(II) perchlorate with N,N′-{bis(pyridin-2-yl)benzylidene}butane-1,4-diamine (bpbd) yielded monoclinic crystals of bluish green [Cu(bpbd)(ClO4)]ClO4 (1), and a similar reaction in presence of azide anion, N3 − formed monoclinic crystals of dark green [Cu(bpbd)(N3)]2ClO4 (2). Crystal data for 1: space group P21/c, Z=4, a=17.3968(4) A, b=9.3182(2) A, c=17.6794(4) A, β=102.149(1)°. The geometry around Cu(II) centre is distorted square pyramidal with axial site occupied by O atom of perchlorate and in plane Cu is bonded to four N atoms of the organic ligand. The intermolecular C–H...π stacking in 1 forms a zigzag chain (1D) supramer. Crystal data for 2: space group C2/c, Z=4, a=22.3109(4) A, b=17.7832(3) A, c=14.3389(2) A, β=92.553(1)°. In dinuclear 2, Cu(II) has tetragonally distorted octahedral geometry coordinated by four N atoms of bpbd, with the fifth and sixth positions occupied by N atoms of two end-on bridging azides. The π...π interaction leads to a two dimensional (2D) sheet within which the counter anions are embedded. Both the compounds 1 and 2 show simple paramagnetism. Cyclic voltammetry and fluorescence spectra are also reported.

A 1:2:2:6 molar ratio of Cd(NO3)2 · 4H2O, Cu(NO3)2 · 3H2O, tris(2-aminoethylamine) (tren) and NH4NCS in aqueous solution at room temperature affords trinuclear complex of the type [Cu2Cd(tren)2(NCS)6] (1). The complex has been characterised using microanalytical, spectroscopic and magnetic results. X-ray diffraction measurements have been made to define the coordination sphere and long-range structure. 1 consists of two pentacoordinated copper(II) occupied by tren N atoms and one bridging SCN− N atom of the central trans-[Cd(NCS)4(SCN)2]4− molecular ion which bridges by the 1,3-thiocyanate. Each of these trinuclear units are engaged in intra as well as intermolecular N–H⋯S hydrogen bonding. Variable-temperature magnetic study shows no significant magnetic interactions among the metal ions.

MnCl2 · 4H2O, Cu(NO3)2 · 3H2O, tris(2-aminoethyl)amine (tren) and NH4NCS in a 1:4:4:10 molar ratio in aqueous solution results a bimetallic compound of the type [Cu(tren)(NCS)]4[Mn(NCS)6] (1) which has been characterized by microanalytical, physicochemical, spectroscopic and magnetic results. The structure of the complex is determined by X-ray diffraction study. Some pertinent crystal data are: monoclinic, space group P21/c, a = 11.0442(9) A, b = 14.4923(12) A, c = 19.2505(16) A, β = 91.95(10)°, and Z = 4. The crystal structure consists of a hydrogen bonded 3D network of [Cu(tren)(NCS)]+ and [Mn(NCS)6]4− ions. Manganese(II) has an MnN6 chromophore bound by six N atoms of the terminal thiocyanates. Each copper(II) centre is five coordinated by one N atom of terminal thiocyanate and four N atoms of the tripod ligand. Four copper(II) units are hydrogen bonded to form a hydrogen bonded tetramer. Each manganese(II) in turn is further engaged in hydrogen bonding to four such tetramers leading to the 3D network. Variable-temperature magnetic study shows no significant magnetic interactions among the metal ions connected by hydrogen bonding.

Cadmium(II) nitrate tetrahydrate – a metal ion template, tris(2-aminoethyl)amine (tren) – a tripodal amine and thiocyanate – a versatile intermediatary in a 3:2:6 mole ratio in water afford a homopolymer, [Cd3(tren)2(NCS)6]n (1). Replacement of two equivalents of cadmium(II) salt by two equivalents of nickel(II) nitrate hexahydrate results in the heteropolymer, [Ni2Cd(tren)2(NCS)6]n (2). Compound 1 crystallizes in the monoclinic C2/c space group with a = 20.3480(17) A, b = 10.8796(9) A, c = 16.3495(10) A, β = 110.009(7)° and Z = 4; 2 crystallizes in the same space group as in 1 with a = 19.584(5) A, b = 11.034(3) A, c = 15.760(4) A, β = 100.712(4)° and Z = 4. 1 and 2 are new examples of homo- and hetero-polymers with the multiconnecting molecular ion bridge [Cd(NCS)6]4− in different geometric configurations. The single crystal X-ray structures of both neutral polymers consist of infinite two-dimensional sheets with two alternating environmentally different octahedral metal ion [M(II) = Ni(II)/Cd(II)] coordination spheres connected by four 1,3-thiocyanato bridging cis-/trans-[Cd(NCS)2(SCN)4]4−. The Cd(1) centres in 1 and 2 with the CdN2S4 chromophore are surrounded by four S atoms of the bridging thiocyanate and two terminal N atoms of the pseudohalide, while the CdN6 chromophore of Cd(2) in 1 and NiN6 chromophore of Ni(1) in 2 are completed by four tren N atoms and two N atoms of the bridging NCS− in cis alignment. In 1, the three tripodal amine N atoms and two bridging S atoms are engaged in strong intermolecular hydrogen bondings, which is responsible for the conformation and stability of the supramolecular network. The absence of such hydrogen bonding in 2 is due to a difference in the orientation of the tripodal amine from that in 1 in the polymeric net. The magnetic property of 2 has been investigated over the 2–300 K temperature range. The feature is characteristic of a Curie law for a typical magnetically isolated nickel(II) ion with very weak antiferromagnetic interactions (J

A novel 1D coordination polymer, [Cu3(imH)8(im)2(ClO4)4]n (1) (imH = imidazole), has been synthesized and X-ray crystallographically characterized. In the long range form 1 affords 3D network through N–H⋯O hydrogen bonding and displays intraligand 1(π–π*) fluorescence and intraligand 3(π–π*) phosphorescence in glassy solution (DMF at 77 K).

One-pot reactions of metal acetate, 2,2′-dipyridylamine (dpa) and NaN3 in a 1:2:2 ratio in aqueous-acetonitrile solutions result in mononuclear complexes of the type [M(dpa)2(N3)2] · H2O [M = Ni (1), Zn (2)]. Structural analyses reveal that both the metal centres adopt distorted octahedral MN6 environments coordinated through four N atoms of two dpa units and two azide N atoms as terminal ligands – the latter occupying mutual cis positions. The crystal packing shows that the mononuclear units self-assemble through hydrogen bonds to afford infinite two-dimensional (2D) sheets. Additionally, the pyridyl planes of adjacent sheets are engaged in face-to-face π⋯π and C–H⋯π interactions leading to a 3D supramolecular continuum. Complexes 1 and 2 exhibit high-energy intraligand 1(π–π*) fluorescence and intraligand 3(π–π*) phosphorescence in glassy solutions (DMF at 77 K). A band (374 nm) observed in their solid-state emission spectra is an excimeric emission originating from an aromatic π⋯π interaction. The role of dpa is highlighted in controlling crystalline aggregation and in arousing luminescence characteristics.

Two different series of cobalt(II) and cobalt(III) complexes of types [Co(L1)(X)2] (1a–1f) and [Co(L2)(X)3] (2a–2f), respectively [L1 = N,N′-(bis(pyridin-2-yl)formylidene)propane-1,3-diamine (pfpd) or N,N′-(bis(pyridin-2-yl)benzylidene)propane-1,3-diamine (pbpd); L2 = (N,N-diethyl,N′-(pyridin-2-yl)formylidene)ethane-1,2-diamine (pfed) or (N,N-diethyl,N′-(pyridin-2-yl)benzylidene)ethane-1,2-diamine (pbed); X = N 3 - , NCS− or NCO−] have been prepared and characterized using microanalytical, spectroscopic, magnetic, electrochemical and other physicochemical results. Structures of one member in each series, viz., [Co(pfpd)(NCS)2] (1c) and [Co(pbed)(N3)3] (2b) are solved by X-ray diffraction measurements for the exact definition of the coordination sphere. Structural analysis reveals cobalt(II) centre in 1c adopts a distorted octahedral environment with a CoN6 chromophore ligated by four N atoms of the tetradentate Schiff base and two N-coordinated NCS− ions in trans orientation. In 2b, the three N atoms of the tridentate Schiff base and three N atoms of three terminal azides are found in meridional arrangement. The organic blockers are folded in ethylenic/propylenic part. Electrochemiocal electron transfer study in MeCN solutions shows cobalt(III)–cobalt(II) response as oxidative in 1 and reductive in 2. Available information shows that the structures 1a, 1b, 1d–1f are cognate with 1c, whereas 2a, 2c, 2d–2f are iso-structural with 2b. All the complexes display intraligand 1(π–π*) fluorescence and intraligand 3(π–π*) phosphorescence in glassy solutions (MeOH at 77 K).

Treatment of Cd(NO3)2 · 4H2O with two equivalents of NH4NCS in combination with two equivalents of imH [imH=imidazole] or one equivalent of pfan [pfan=((pyridin-2-yl)formylidene)aniline] results neutral 1D polymers of the type [Cd(imH)2(NCS)(SCN)]n (1) or [Cd(pfan)(NCS)(SCN)]n (2). X-ray structure determinations show that in both polynuclear 1 and 2, octahedral CdII ions occupy centre of symmetry with a CdN4S2 chromophore. The metal ions are linked through N and S atoms of NCS− alternately in doubly bridged end-to-end fashion; two mutually trans N atoms of monodentate imH units complete hexacoordination of each metal centre in 1. Similar NCS-bibridging chain is present in 2 with one bidentate (N,N) Schiff base chelator (pfan) in cis orientation. The 1D chains in 1 are further engaged in intermolecular hydrogen bonding (N–H⋯S) between N of imH and coordinated S of NCS− along with aromatic π–π stacking of imH moieties that constrain the 1D chains to lie in bc-plane, which are further linked via C–H⋯π interactions. In 2, 1D chains participate in two kinds of π–π interactions. Supramers 1 and 2 display intraligand 1 ( π – π * ) fluorescence and intraligand 3 ( π – π * ) phosphorescence in glassy solutions (MeOH at 77 K).

The synthetic details, characterization data and single crystal X-ray structural analyses of [Zn(dpa)(N3)2] (1) and [Zn(dpa)(N3)(NO3)]2 (2) (dpa=2,2′-dipyridylamine) are described. Structural study reveals that the zinc(II) centre in 1 is in a pseudotetrahedral ZnN4 environment ligated by two terminal azide N atoms and two pyridine N atoms of the chelator. The coordination polyhedron around each metal ion in dinuclear 2 is best described as a ZnN4O2 distorted octahedron linked by two end-on azido bridges. The mononuclear units in 1 are engaged in bifurcated intermolecular hydrogen bonding (N–H…N) between amine N of dpa and coordinated N of azide along with aromatic π–π stacking leading to a 2D sheet. In 2, the dinuclear units participate in intermolecular N–H…O hydrogen bonding between amine N of dpa and bound O of bidentate nitrate in combination with π–π interactions resulting to a 3D supramolecular continuum. 1 and 2 display high energy intraligand 1(π–π*) fluorescence and intraligand 3(π–π*) phosphorescence in glassy solutions (DMF at 77 K). A band (372 nm) observed for both 1 and 2 in their solid-state emission spectra is an excimeric emission arising due to aromatic π–π interaction. The role of dpa, a tailored diimine (–N  C | –NH– C |  N–) in 1 and 2 is discussed towards functionalisation on crystal engineering and luminescence behaviour.

Department of Chemistry, The University of Burdwan, Burdwan-713 104, India E-mail : barin_1 @yahoo.co.uk Fax : 91-342-530452 Manuscript received 27 August 2001, revised 11 February 2002, accepted 25 April 2002 Eight mixed ligand compounds of osmium(II), -(III), -(IV) of general formula, [Os(dpya)L2]z+ [dpya = 2,2'-dipyridylamine; L = 2-(phenylazo)pyridine (L1), 2-(m-tolylazo)pyridine (L2), 2,2'-bipyridyl (L3), quinolin-8-olate (L4) or 2-methylquinolin-8- olate (L5); ζ = 1-3] have been prepared, isolated as their perchlorates. The complexes exhibit several spin-allowed and spin-forbidden charge-transfer transitions in the 200-1000 nm region. In MeCN solutions the chelates display OsIV'-OsIII and OsIII- OsII couples. The stability of metal oxidation levels is discussed in terms of the electrochemical results and correlated to the π-acceptor properties of these ligands. On the negative side of SCE successive ligand reductions in L1—L3 complexes are observable.