Tuning Structures And Emissive Properties In A Series Of Zn(Ii) And Cd(Ii) Coordination Polymers Containing Dicarboxylic Acids And Nicotinamide Pillars

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

Six Flexible and Rigid Co(II) Coordination Networks with Dicarboxylate and Nicotinamide-Like Ligands: Impact of Noncovalent Interactions in Retention of Dimethylformamide Solvent

Six mixed-ligand Co­(II) coordination polymers, {[Co­(adi)­(iso-nia)₂]·dmf}_<i>n</i> (<b>1</b>), [Co­(adi)­(iso-nia)₂]_<i>n</i> (<b>2</b>), {[Co₂(suc)­(ac)₂(iso-nia)₄]­[Co₂(suc)­(sucH)₂(iso-nia)₄]­·2dmf}_<i>n</i> (<b>3</b>), [Co­(adi)­(nia)₂]_<i>n</i> (<b>4</b>), {[Co­(bdc)­(nia)₂]­·dmf}_<i>n</i> (<b>5</b>), and {[Co­(mal)­(S-nia)­(H₂O)]·dmf}_<i>n</i> (<b>6</b>), 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 <b>1</b>, <b>2</b>, and <b>3</b> represent one-dimensional coordination polymers, whereas <b>4</b>, <b>5</b>, and <b>6</b> exhibit two-dimensional structures. The coordination arrays in <b>1</b>–<b>5</b> are built from the similar [Co₂(COO)₂] binuclear clusters, while framework <b>6</b> 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 <b>1</b>, <b>3</b>, <b>5</b>, and <b>6</b> host dmf solvent via NH···O hydrogen bonding and π–π stacking interactions with the coordination networks. Details of the reversible dmf release–uptake by <b>1</b> and <b>2</b>, and contribution of hydrogen bonding in stabilization of the solvent-free structures <b>2</b> and <b>4</b> are discussed. All new solids were characterized by IR spectroscopy and thermogravimetric analysis, while magnetic measurements are reported for compounds <b>1</b>, <b>5</b>, and <b>6</b>. The magnetic data show the typical behavior of Co­(II) ions originating from pronounced zero-field splitting within the ground state with contributing effects from weak antiferromagnetic exchange interactions