A p‐Quinodimethane‐Bridged Porphyrin Dimer

Abstract

A p-quinodimethane (p-QDM)-bridged porphyrin dimer 1 has been prepared for the first time. An unexpected Michael addition reaction took place when we attempted to synthesize compound 1 by reaction of the cross-conjugated keto-linked porphyrin dimers 8a and 8b with alkynyl/aryl Grignard reagents. Alternatively, compound 1 could be successfully prepared by intramolecular Friedel-Crafts alkylation of the diol-linked porphyrin dimer 14 with concomitant oxidation in air. Compound 1 shows intense one-photon absorption (OPA, λ(max)=955 nm, ε=45400 M(-1) cm(-1)) and a large two-photon absorption (TPA) cross-section (σ((2))(max)=2080 GM at 1800 nm) in the near-infrared (NIR) region due to its extended π-conjugation and quinoidal character. It also exhibits a short singlet excited-state lifetime of 25 ps. The cyclic voltammogram of 1 displays multiple redox waves with a small electrochemical energy gap of 0.86 eV. The ground-state geometry, electronic structure, and optical properties of 1 have been further studied by density functional theory (DFT) calculations and compared with those of the keto-linked dimer 8b. This research has revealed that incorporation of a p-QDM unit into the porphyrin framework had a significant impact on its optical and electronic properties, leading to a novel NIR OPA and TPA chromophore.

Intermacrocyclic Interaction Triggers Facile One‐Pot Synthesis of a Chlorin–Porphyrin Heterodimer

“…Although the HOMO/HOMO‐1 and the LUMO/LUMO+1 orbital pairs are degenerate in M 2 DEP, the degeneracy is somewhat lifted in the heterodimer as the orbital contribution from each macrocyclic subunit interacts through the π‐system of the bridge. The substantial orbital energy splitting in the frontier region and a decrease in the HOMO–LUMO gap are strong indicators of electronic interactions, between the two rings in the chlorin–porphyrin heterodimer M 2 DEPR⋅X.…”

Modern zethrene chemistry

“…It also exhibits large TPA cross section ( (2) max = 1300 GM at 1800 nm). Similarly, a p-QDM bridged porphyrin dimer 73 34 shows an intense absorption at 955 nm ( = 4.54 × 10 4 (mol/L) −1 cm −1 ). However, it was proved to have a closed-shell ground state.…”

A Diradical Approach towards BODIPY‐Based Dyes with Intense Near‐Infrared Absorption around λ=1100 nm

“…On the basis of these values, optical energy gaps of 0.80 eV and 0.79 eV,respectively,could then be roughly estimated. Thee stimated electrochemical energy gaps (E g EC = 0.75 eV for BD-1,0 .72 eV for BD-2)a re consistent with the optical energy gaps.C ompared with other typical closed-shell p-conjugated systems,s uch as ab enzo-[b]-fused BODIPY dimer (l max abs = 629 nm, e = 1.02 10 5 m À1 cm À1 ), [11] ab enzo-[a]-fused BODIPY dimer (l max abs = 758 nm, e = 1.9 10 5 M À1 cm À1 ), [12] and a p-QDMbridged porphyrin dimer (l max abs = 955 nm, e = 4.54 10 4 M À1 cm À1 ), [13] BD-1 and BD-2 showed bathochromic shifts of nearly 500 nm, 350 nm, and 150 nm, respectively, despite their similar p-conjugation size.Dyes BD-1 and BD-2 are rare examples of NIR dyes with very intense absorption around l = 1100 nm and may find practical application in Nd:YAG 1064 nm laser protection. Thee stimated electrochemical energy gaps (E g EC = 0.75 eV for BD-1,0 .72 eV for BD-2)a re consistent with the optical energy gaps.C ompared with other typical closed-shell p-conjugated systems,s uch as ab enzo-[b]-fused BODIPY dimer (l max abs = 629 nm, e = 1.02 10 5 m À1 cm À1 ), [11] ab enzo-[a]-fused BODIPY dimer (l max abs = 758 nm, e = 1.9 10 5 M À1 cm À1 ), [12] and a p-QDMbridged porphyrin dimer (l max abs = 955 nm, e = 4.54 10 4 M À1 cm À1 ), [13] BD-1 and BD-2 showed bathochromic shifts of nearly 500 nm, 350 nm, and 150 nm, respectively, despite their similar p-conjugation size.Dyes BD-1 and BD-2 are rare examples of NIR dyes with very intense absorption around l = 1100 nm and may find practical application in Nd:YAG 1064 nm laser protection.…”