Comparative study of two new grid complexes: synthesis, X-ray structure characterization, thermogravimetric, and spectroscopic properties

The synthesis and characterization of two new grid complexes, [Ni-4(L)(4)(DMF)4]center dot 2H(2)O (1) and [Mn-4(L)(4)(DMF)(4)] (2) (where L is the anion of 3,5-dichlorosalicylaldehyde pyridine-2-formyl hydrazone), were investigated. X-ray crystal structure analysis reveals that the metal centers in both complexes exhibit slightly distorted square-bipyramidal coordination geometry. The dominating interaction of two adjacent grids for 1 and 2 is Cl center dot center dot center dot H hydrogen bonds. The halogen-hydrogen bond is a key factor to stabilize the crystal structure of chloro-substituted grid compounds. Thermogravimetric curves of 1 and 2 exhibit distinct weight loss stages at different temperatures and reflect the thermal stability of the complexes. Both UV-visible and fluorescence spectra of 1 and 2 indicate they have a stronger conjugated system and the same significant quenching ability compared with H2L. The ESI-MS spectra of 1 and 2 prove that the tetranuclear grids decompose in methanol/water solution.