| The synthesis and physical characterizations are reported for a series of peripherally functionalized porphyrazines (pz's) with one metal ion incorporated into the pz core, M1, and a second metal ion M2 bound to a bis(5-tert-butyl-salicylidenimine) chelate built onto two amino nitrogen attached to the peripheral carbons of a pz pyrrole. Six solubilizing group (R, either propyl (Pr) or 3,4,5-trimethoxyphenyl (TMP) group) are attached to the remaining carbons of the periphery. These compounds are denoted 1[M1; M2; R] (Chapter 2--4). They are prepared from precursor pz's with a selenodiazole ring; the precursors are deprotected to form the diamino pz, which reacts with two moles of 5-tert-butyl-2-hydroxybenzaldehyde to form the Schiff base pz; this is metallated to form 1[M1; M 2; R]. Several crystal structures are presented. The EPR spectra of the M1-M2 isomers prepared with Cu(II) ( S = 1/2) and ClMn(III) (S = 2) ions, 1[ClMn; Cu; Pr] and 1[Cu; ClMn; TMP], are a superposition of spectra expected for the S = 3/2 and S = 5/2 total-spin manifolds that result from strong Heisenberg coupling between the partner spins. The exchange splitting between the two manifolds, as determined by temperature-dependent magnetic susceptibility measurements, is the same, within error, for the two M1-M2 isomers, Delta/ kB ≈ 20--25K, which suggests a purely sigma-pathway for exchange coupling. The magnetic susceptibility experiments reveal that there is much stronger interaction between the metal centers in 1[Cu; Cu; R] than in 1[Cu; VO; R], while the interaction is weaker in 1[ClMn; Cu; Pr] than in 1[ClMn; VO; Pr]. We explain the intramolecular interaction in terms of the symmetry of the magnetic orbitals of the metal ions that are involved in the sigma-pathway for exchange coupling.; As a next step toward generating high-spin molecules, a few trimetallic complexes 1[M1; M2; M2] with two peripheral Schiff base units attached in the cis-configuration were prepared from pzs with two cis-selenodiazole ring; the remaining two pyrroles are functionalized with R = TMP. EPR spectra show that there is spin coupling between two peripheral M2 metal ions, and between the core and the peripheral metal ions. |
