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Five new transition metal coordination compounds based on pyrazinecarboxamide and dicarboxylic acids have been prepared, and their structures have been characterized by IR spectroscopy and single crystal X-ray diffraction. The crystalline solids include one dinuclear compound [Cu2(mal)2(pca)2(H2O)2]·H2O (1), three one-dimensional coordination polymers [M(mal)(pca)(H2O)]n M = Co(II), Zn(II) (2, 3), [Cu2(CH3COO)4(pca)]n (4) and one two-dimensional coordination polymer [Cd(bdc)(pca)(H2O)]n (5), where pca = pyrazinecarboxamide, H2mal = malonic acid and H2bdc = 1,4-benzenedicarboxylic acid. The pca coordinates to the metal centers as a neutral ligand in chelating (1, 2, 3), bidentate bridging (4) and monodentate modes (5), while the bidentate acetate, malonate and benzenedicarboxylato anionic ligands provide extensions of structures. The new compounds 1, 3 and 5 reveal violet and ultraviolet luminescence upon excitation with ultraviolet light.

New coordination polymers are reported. All polymers were prepared from a blend of four dicarboxylic acids, three neutral nicotinamide ligands, and Zn(II) or Cd(II) salts. The acids included: malonic (H2mal), succinic (H2suc), adipic (H2adi), and 1,4-benzenedicarboxylic (H2bdc) acids, with all of them varying in length and rigidity of the carbon skeletons. The neutral ligands included two positional isomers, isonicotinamide (iso-nia) and nicotinamide (nia), and a nia thio-analogue, thionicotinamide (S-nia). The preparation resulted in eight Cd(II) and four Zn(II) coordination polymers: [Cd2(suc)(sucH)2(nia)4]n (1), {[Cd(suc)(nia)3]·H2O·dmf}n (2), {[Cd(adi)(iso-nia)2]·dmf}n (3), [Cd(adi)(iso-nia)2]n, (4), {[Zn(mal)(iso-nia)(H2O)]·dmf}n (5), {[Cd(mal)(iso-nia)(H2O)]·dmf}n (6), {[Zn(mal)(nia)(H2O)]·dmf}n (7), {[Cd(mal)(nia)(H2O)]·dmf}n (8), {[Zn(mal)(S-nia)(H2O)]·dmf}n (9), {[Zn(bdc)(nia)2]·dmf}n (10), {[Cd(bdc)(nia)2]·dmf}n (11), and nicotinamide-free {[Cd(bdc)(H2O)2(dmf)]·dmf}n (12). Compounds 1–4 and 12 consist of one-dimensional arrays, while compounds 5–11 are two-dimensional coordination arrays. The coordination cores in 1, 3, 4, 10, and 11 present {M2(COO)2} (M = Zn, Cd) binuclear clusters, while the networks of 2, 5–9 and 12 are built on mononuclear metal nodes with nicotinamide ligands acting as double or single pillars. The structure-confirmed single crystal to single crystal transformation of 3 into 4 was detected and reported. While 1 and 4 are solvent-free apohosts, the remaining solids acted as hosts of water and dmf solvent which are accommodated in the crystal lattices as coordinated ligands or lattice solvents. The new solids were characterized by IR spectroscopy, thermogravimetric analysis, and single-crystal and powder X-ray diffraction methods. The luminescence properties of six as-synthesized coordination polymers and of some activated products are reported. The influence of the metal, ligand, and solvent on tuning the structures and emission properties was monitored, and the most impressive effects were interpreted with the help of TD-DFT computations.

The reaction of a ditopic ligand, 1,4-benzenedicarboxylic acid (H 2 bdc) with Co(CH 3 COO) 2 ·4H 2 O in solution resulted in a solvent-rich layered coordination polymer with the composition {[Co 2 (μ 2 -OH 2 )(bdc) 2 (dmf) 2 (H 2 O) 2 ]·(dmf)·3(H 2 O)} n ( 1 ) whose crystal structure was determined by single crystal X-ray diffraction. The compound is built on the binuclear {Co 2 (μ 2 -OH 2 )(COO) 2 } metal clusters, where each Co(II) atom is coordinated by six oxygen atoms in a distorted octahedral arrangement. The crystal lattice of 1 hosts the dmf and water solvent molecules via the OH⋯O hydrogen bonding with coordination network. The easy destruction of the crystals due to the partial solvent loss occurs rapidly in ambient conditions and is confirmed by the TGA data.

Six coordination compounds based on 4,4′-diaminodiphenylmethane (dadpm) and different salts (acetates, nitrates and perchlorates) of four (Ni, Co, Zn, Cd) transition metals have been prepared and characterized by IR spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction methods. The crystalline solids include four monomers: [Co(dadpm)2(CH3COO)2(H2O)2] (1), [Cd(dadpm)2(CH3COO)2(H2O)2] (2), [Zn(dadpm)4(H2O)2](NO3)2(H2O)2 (3), [Ni(dadpm)3(dmf)(H2O)2](ClO4)2(dadpm)(H2O) (4), and two one-dimensional coordination polymers: {[Cd(dadpm)2(H2O)(ClO4)](ClO4)}n (5) and {[Cd(dadpm)4](ClO4)2}n (6). The transition metals used in this study accommodate two, three, four and six dadpm ligands in the coordination cores. The luminescence properties for six coordination compounds are reported.

Heating of a pink two-dimensional Co(II) coordination network {[Co2(μ2-OH2)(bdc)2(S-nia)2(H2O)(dmf)]·2(dmf)·(H2O)}n (1) built from 1,4-benzenedicarboxylic acid (H2bdc) residues and thionicotinamide (S-nia) ligands initiates a single-crystal-to-single-crystal transition accompanied by removal of both coordinated and co-crystallized solvents. In the dry blue form, [Co(bdc)(S-nia)]n (dry_1), the Co(II) centers changed from an octahedral to a square pyramidal configuration.

A new three-dimensional coordination polymer, {[Co(μ2-H2O)(bdc)(H2O)(dmf)]·0.5H2O}n (1), was obtained as a by-product in the synthesis of the laminar solid {[Co2(μ2-H2O)(bdc)2(S-nia)2(H2O)(dmf)]·(dmf)2·H2O}n (2) (where H2bdc = 1,4-benzenedicarboxylic acid, S-nia = thionicotinamide, dmf = N,N′-dimethylformamide). The three-dimensional network in 1 is organized of Co(II) atoms in O6 octahedral coordination environments separated by μ2-water molecules in coordination chains. The bdc2− anions coordinate in monodentate mode and also act as bridging ligands that extend the structure in two other directions. The coordination cores of two crystallographically different Co(II) atoms are completed by either two dmf or two water molecules. The rhombohedral open channels contain water molecules. The evacuation of solvents from 1 occurs as a single crystal to single crystal transformation and results in MOF-71, [Co(bdc)(dmf)]n, whose structure was confirmed by single crystal X-ray diffraction.

Six mixed-ligand Co(II) coordination polymers, {[Co(adi)(iso-nia)2]·dmf}n (1), [Co(adi)(iso-nia)2]n (2), {[Co2(suc)(ac)2(iso-nia)4][Co2(suc)(sucH)2(iso-nia)4]·2dmf}n (3), [Co(adi)(nia)2]n (4), {[Co(bdc)(nia)2]·dmf}n (5), and {[Co(mal)(S-nia)(H2O)]·dmf}n (6), were synthesized and characterized by single crystal X-ray analysis. They are based on four dicarboxylic acids, namely, malonic (H2mal), succinic (H2suc), adipic (H2adi), and 1,4-benzenedicarboxylic (H2bdc) acids, as well as three nicotinamide-like ligands, isonicotinamide (iso-nia), nicotinamide (nia) and thionicotinamide (S-nia). Compounds 1, 2, and 3 represent one-dimensional coordination polymers, whereas 4, 5, and 6 exhibit two-dimensional structures. The coordination arrays in 1–5 are built from the similar [Co2(COO)2] binuclear clusters, while framework 6 is based on mononuclear metal nodes. All crystal lattices are supported by hydrogen bonding with nicotinamide-like ligands acting as pillars or dangling terminal ligands. Four crystal lattices...