Periphery-Fused Chiral A2B-Type Subporphyrin

Abstract

Despite significant interest, the chiroptical properties of subporphyrins have rarely been investigated because chiral subporphyrins are elusive. Here, inherently chiral subporphyrins are elaborated by forming a fused pyran ring at the periphery of an A2B-type meso-aryl-substituted subporphyrin. Their circular dichroism (CD) properties are largely affected by the peripheral substituents and the dihedral angles between the meso-aryl substituents and the subporphyrin core: the β-perbromo subporphyrin with an orthogonal arrangement of the meso-phenyl substituents to the subporphyrin core exhibits weak CD signals corresponding to the Q bands, whereas the unsubstituted species with smaller dihedral angles shows relatively intense CD signals. A detailed structure–property relationship of these chiral subporphyrins was elucidated by time-dependent (TD) DFT calculations. This study reveals that the CD properties of chiral subporphyrins can be controlled by peripheral substitution and meso-aryl substituents.

Recent advances in subphthalocyanines and related subporphyrinoids

“…628 A related SubP 564 (Scheme 49) bearing a fused pyran ring has been synthesized in 14% overall yield by cleavage of the methoxy group of SubP 431 with BBr 3 , giving a hydroxy group, followed by perbromination and intramolecular ether formation in the presence of potassium carbonate. 633 Similarly, SubP 562 , containing two fused dihydroquinoline rings, has been obtained by a double cyclization of the aryl groups in the β,β-diiodo- meso -diarylamino subporphyrin SubP 561 . The latter entails a radical-nucleophilic substitution reaction (SRN1) involving stable radical intermediates that are generated by single electron transfer from tert -butoxide or diarylamide anions to the SubP, with concomitant loss of iodide ions of 561 .…”