ESR STUDY OF COBALT(II) TETRAKIS(N-METHYL-4-PYRIDINIUMYL)PORPHYRIN AND COBALT(II) TETRASULFOPHTHALOCYANINE INTERCALATED IN LAYERED ALUMINOSILICATES AND A LAYERED DOUBLE HYDROXIDE

The orientation, hydration state, and electronic properties of Co(II) tetrakis(N-methyl-4-pyridiniumyl) porphyrin (CoTMPyP) cation and Co(II) tetrasulphophthalocyanine (CoPcTs) anion, intercalated in crystalline negatively charged layered aluminosilicates and positively charged layered double hydroxide (LDH), respectively, were studied in the presence and absence of water by electron spin resonance (ESR), electron absorption spectroscopy, and X-ray diffraction (XRD). When intercalated on the low charge density clay hectorite, CoTMPyP orients with the plane of the porphyrin parallel to the clay layers, The g tensors, in both the wet and dry states (g parallel to = 1.88, g perpendicular to = 3.10), are indicative of CoTMPyP interacting with charge-deficient siloxane oxygens on the hectorite surface and having no water in axial coordination sites. Intercalation of CoTMPyP into the high-charge density fluorohectorite causes the porphyrin ring to orient at a 27 degrees angle to the clay layers with water molecules coordinated to Co(II) (g parallel to = 2.03, g perpendicular to 2.42). Vacuum dehydration decreases the basal spacing of CoTMPyP-fluorohectorite from 19.6 to 17.6 Angstrom, causing a rearrangement of the intercalated CoTMPyP into a staggered bilayer with no axial water bound to Co(II). The basal spacing (23.7 Angstrom) of CoPcTs-LDH intercalate is consistent with an edge on orientation of the phthalocyanine. The ESR spectra (g parallel to = 2.05, g perpendicular to = 2.45) indicate Co(II) has water in axial coordination site(s) when wet or air-dried. Upon vacuum dehydration, the spacing of the LDH intercalate does not change, but the intercalated Co macrocycle becomes ESR-silent due to Co(II)-Co(II) interactions. Third-order perturbation calculations indicate that the excited singlet state is about 3 times higher in energy for CoTMPyP-hectorite than for the CoTMPyP-fluorohectorite and CoPcTs-LDH before vacuum dehydration.