Discotic liquid crystalline Octa(2-ethylhexyloxy) and Octa(1,4,7,10-tetraoxaundecyl) metallophthalocyanines; Syntheses, characterizations and applications

Abstract

Phthalocyanines (Pcs) are synthetic analogues of porphyrins with a structure similar to that of hemoglobin and chlorophyll. Octa(2-ethylhexyloxy) phthalocyanines and octa(1,4,7,10-tetraoxaundecyl) phthalocyanines where hydrogen, Cu, Co, Pt, and Pb are in core are synthesized. The structures are identified by elemental analysis, continuous flow liquid secondary ion mass spectroscopy, $^{1}$H NMR, $^{13}$C NMR, solid state $^{13}$C NMR, UV and IR. The phase transitions of octa(2-ethylhexyloxy) $H_{2}Pc$ and CuPc occur at 170, 223, 270℃ and 204, 242, 290℃, and their mesomorphic structures of $H_{2}Pc$ and CuPc are found as $D_{t}$ and $N_{D}$. The phase transition of octa(2-ethylhexyloxy) PtPc and PbPc occur at 205℃ and 79℃, and their mesomorphic structures of PtPc and PbPc are found as $D_{ob}$ and $D_{s}$. Also, the mesomorphic structures of octa(1,4,7,10-tetraoxaundecyl) phthalocyanines are found as $D_{rh}$ ($H_{2}Pc$), $D_{hd}$ (CuPc), $D_{hd}$ (PtPc), and $D_{ob}$ (PbPc) between -100℃ and 250℃. The aggregation phenomena of $H_{2}Pc$, CuPc, and PtPc with 1,4,7,10- tetraoxaundecyl side chains are studied with the absorption spectra changed from an estimated monomeric form(660 and 700 nm for $H_{2}Pc$, 680 nm for CuPc, and 650 nm for PtPc) to a dimeric form (about 630 nm for all Pcs) in diluted solutions ($10^{-4}$ - $10^{-8}$ M) of benzene and acetone. The obtained equilibrium constants of $H_{2}Pc$, CuPc, and PtPc are $2.5-3.7×10^5 M^{-1}$ (benzene) and $1.25-2.12×10^6 M^{-1}$ (acetone), and their Gibbs free energies of dimerization are 30.9 - 31.8 KJ/mol (benzene) and 34.8 - 36.1 KJ/mol (acetone) at 25℃. The electrical conductivity of octa(2-ethylhexyloxy) dihydrogen phthalocyanine was measured as $6.0×10^6㎡/VㆍS$ at 180℃. Octa(2-ethylhexyloxy) phthalocyanines with 2H, Cu, Co, Pt, Pb in Pc core are used as chemical sensor for $NO_2$ gas detection, and $H_2 Pc$ and CuPc have good sensitivities and selectivities to $NO_2$ gas and they can be recovered by...