Pyrrolic-identity-gated β,β-annulation in N-confused hexaphyrins: orbital modulation and metal-amplified near-infrared absorption.

β,β-Annulation is an effective strategy for extending the π-conjugation of porphyrinoids. However, in N-confused expanded porphyrins, the electronic consequence of annulation can be gated by the identity of the fused pyrrolic unit. Herein, DFT and TD-DFT calculations were performed to investigate naphthalene- and anthracene-fused N-confused hexaphyrins, together with their bis-Ni(II), bis-Pd(II), and bis-Pt(II) complexes. In the free-base systems, imine-type trans annulation is thermodynamically preferred. Nevertheless, the fused pyrrolic identity reorganizes the π-electronic topology and frontier-orbital composition; in the amine-type structures, this reorganization is associated with smaller HOMO-LUMO gaps and more red-shifted NIR absorption. Excited-state analyses show that the low-energy states are predominantly based on macrocycle-centred π-π* excitation: imine-type systems contain only a weak PAH-to-macrocycle polarization component, whereas net interfragment transfer is essentially absent for the amine-type systems. Upon bis-metal coordination, the relative stability order of the two fixed annulation-connectivity isomers is reversed for all three group 10 metals. The S0 → S1 absorption of the trans-naphthalene-fused complexes is tunable from 1279 to 1595 nm by combining annulation mode and metal identity, with the A-derived/I-derived wavelength difference increasing with metal identity and metal-ligand orbital mixing. These findings establish pyrrolic identity, N-confusion degree, and metal identity as cooperative parameters for tuning the π-electronic structure and NIR absorption of expanded porphyrinoids and show that metal coordination can reorganize the relative stability of the two annulation-connectivity frameworks.