Structure-sensitive marker bands of metallocorroles: A resonance Raman study of manganese and gold corrole derivatives

Soret-excited resonance Raman spectra (λ_ex 413.1 nm) were acquired for manganese(III) and gold(III) tris(pentafluorophenyl)corrole, each as four different isotopomeric samples: natural abundance, fully pyrrole-¹⁵N-substituted, fully meso-¹³C-substituted, and fully pyrrole-¹⁵N-meso-¹³C-substituted. The spectra were modeled with density functional theory-based vibrational analyses, which in general did an excellent job of reproducing both the absolute frequencies and isotope shifts. The results led to the assignment and visualization of approximately 10 prominent Raman bands. A key finding was that the bands could be categorized into two broad classes: Class A, exhibiting large ¹⁵N isotope shifts, assignable to vibrations with predominant C_α-N character, and Class B, exhibiting large meso-¹³C isotope shifts, assignable to vibrations with predominant C_α-C_meso character. Preliminary evidence suggests that the class A bands may serve as core size markers, while class B bands may correlate with the innocence or otherwise of the corrole macrocycle.