2,2′-Biphenyldiol-bridged bis(free base porphyrin): synthesis and chiroptical probing of asymmetric amino alcohols

A new type of bis(free base porphyrin) 1, in which two porphyrin units are attached to the 5,5′-positions of the 2,2′-biphenyldiol group, has been synthesized. It exhibits exciton-coupled bisignate circular dichroism (CD) spectra upon interaction with chiral amino alcohols. The chiral information from the stereogenic center of amino alcohols is introduced as a twist of the porphyrin units in 1 via hydrogen bonding interactions, detectable by the signal in the CD spectrum. Based on these findings, it is proposed that 1 should serve as a reporter unit of chiral sensor systems.