VARIABLE-TEMPERATURE FE-57 MOSSBAUER STUDIES OF THE ALPHA-PHASE AND BETA-PHASE OF IRON PHTHALOCYANINE

Iron phthalocyanine (FePc) has been studied using Fe-57 Mossbauer spec troscopy, to obtain information which helps in understanding the gas-s ensing properties of phthalocyanines. The isomer shift values of the a lpha and beta phases (0.46 and 0.49 with respect to alpha-Fe) occur be tween high-spin and low-spin iron(II) ion. The quadrupole values (2.50 and 2.62) are characteristic of high-spin iron(II). The variable-temp erature studies have determined different Debye temperatures (theta(D) ) and recoil fractions at room temperature (f(300)) for the alpha and beta phases, respectively: theta(D) = 143 and f(300) = 0.14; theta(D) = 199 and f(300) = 0.36. This indicates a more rigid structure for the beta-phase, consistent with the presence of the two additional nitrog en interactions, absent in the alpha-phase, giving an octahedral struc ture.