10.1021/ic0501420.s001 Sachindranath Pal Sachindranath Pal Anil Kumar Barik Anil Kumar Barik Samik Gupta Samik Gupta Arijit Hazra Arijit Hazra Susanta Kumar Kar Susanta Kumar Kar Shie-Ming Peng Shie-Ming Peng Gene-Hsiang Lee Gene-Hsiang Lee Ray J. Butcher Ray J. Butcher M. Salah El Fallah M. Salah El Fallah Joan Ribas Joan Ribas Copper(II) Mediated Anion Dependent Formation of Schiff Base Complexes<sup>†</sup> American Chemical Society 2005 BF terminal copper atoms N 4 O chromophore HL copper atoms H 2 L 1 MPA UV 2 equiv amount N 5 chromophore 2 equiv N 4 Cl chromophore N 4 O 2 chromophore Cu DAP Schiff base IR 1 equiv center ClO 4 2005-05-30 00:00:00 Dataset https://acs.figshare.com/articles/dataset/Copper_II_Mediated_Anion_Dependent_Formation_of_Schiff_Base_Complexes_sup_sup_/3284149 A tetranuclear mixed ligand copper(II) complex of a pyrazole containing Schiff base and a hydroxyhexahydropyrimidylpyrazole and copper(II) and nickel(II) complexes of the Schiff base having N-donor atoms have been investigated. A 2 equiv amount of 5-methyl-3-formylpyrazole (MPA) and 2 equiv of 1,3-diamino-2-propanol (1,3-DAP) on reaction with 1 equiv of copper(II) nitrate produce an unusual tetranuclear mixed ligand complex [Cu<sub>4</sub>(L<sub>1</sub>)<sub>2</sub>(L<sub>2</sub>)<sub>2</sub>(NO<sub>3</sub>)<sub>2</sub>] <b>(1),</b> where H<sub>2</sub>L<sub>1</sub> = 1,3-bis(5-methyl-3-formylpyrazolylmethinimino)propane-2-ol and HL<sub>2</sub> = 5-methyl-3-(5-hydroxyhexahydro-2-pyrimidyl)pyrazole. In contrast, a similar reaction with nickel(II) nitrate leads to the formation of a hygroscopic intractable material. On the other hand, the reaction involving 2 equiv of MPA and 1 equiv each of 1,3-DAP and various copper(II) salts gives rise to two types of products, viz. [Cu(T3-porphyrinogen)(H<sub>2</sub>O)]X<sub>2</sub> (X = ClO<sub>4</sub>, NO<sub>3</sub>, BF<sub>4</sub> (<b>2</b>)) (T<sub>3</sub>-porphyrinogen = 1,6,11,16- tetraza-5,10,15,20- tetrahydroxy-2,7,12,17-tetramethylporphyrinogen) and [Cu(H<sub>2</sub>L<sub>1</sub>)X]X·H<sub>2</sub>O (X = Cl (<b>3</b>), Br (<b>4</b>)). The same reaction carried out with nickel(II) salts also produces two types of compounds [Ni(H<sub>2</sub>L<sub>1</sub>)(H<sub>2</sub>O)<sub>2</sub>]X<sub>2</sub> [X = ClO<sub>4</sub> (<b>5</b>), NO<sub>3</sub> (<b>6</b>), BF<sub>4</sub> (<b>7</b>)] and [Ni(H<sub>2</sub>L<sub>1</sub>)X<sub>2</sub>]·H<sub>2</sub>O [X = Cl (<b>8</b>), Br (<b>9</b>)]. Among the above species <b>1</b>, <b>3</b>, and <b>5</b> are crystallographically characterized. In <b>1</b>, all four copper atoms are in distorted square pyramidal geometry with N<sub>4</sub>O chromophore around two terminal copper atoms and N<sub>5</sub> chromophore around two inner copper atoms. In <b>3</b>, the copper atom is also in distorted square pyramidal geometry with N<sub>4</sub>Cl chromophore. The nickel atom in <b>5</b> is in a distorted octahedral geometry with N<sub>4</sub>O<sub>2</sub> chromophore, where the metal atom is slightly pulled toward one of the axial coordinated water molecules. Variable-temperature (300 to 2 K) magnetic susceptibility measurements have been carried out for complex <b>1. </b>The separations between the metal centers, viz., Cu(1)···Cu(2), Cu(2)···Cu(2A), and Cu(2A)···Cu(1A) are 3.858, 3.89, and 3.858 Å, respectively. The overall magnetic behavior is consistent with strong antiferromagnetic interactions between the spin centers. The exchange coupling constants between Cu(1)···Cu(2) and Cu(2)···Cu(2A) centers have turned out to be −305.3 and −400.7 cm<sup>-1</sup>, respectively, resulting in a <i>S</i> = 1/2 ground state. The complexes are further characterized by UV−vis, IR, electron paramagnetic resonance, and electrochemical studies.