Semiconductive properties of zinc(II)-porphyrinic coordination arrays

Two coordination polymers, 1 and 2 were developed utilizing the favorable hexacoordinated zinc(II) center in porphyrins. Single crystal X-ray structure analysis revealed that 1 forms one dimensional array whereas 2 display three dimensional network structures. Scanning tunnelling microscopic studies have shown that compounds 1 and 2 can tunnel the electric current through the crystal lattice indicating the conducting behavior of these solid crystals. The self-assembled solid crystal 2 has shown uniform conductance whereas 1 does not. The thermal stability of these crystals were determined by TGA analysis and found to be stable up to a higher temperature of 400 degrees C. A temperature dependent current-voltage analysis were also performed and the results indicate that the conductivity of crystals 1 and 2 increases with increase in temperature. It is found that the temperature coefficient of resistance (alpha) at 100 degrees C for 1 and 2 as -0.009 and 0.017 K-1.