Tailored Solvatochromic NIR Phosphorus-Chromophores via Selective P−N and P−C Chemistry in P-Heteropines

Abstract

Herein we report selective P–C and P–N chemistry as a new synthetic tool for constructing phosphorus (P)-chromophores with rich chemical structures. Our studies reveal that isomeric structures significantly influence the chemical structure and electronic communication of P-heteropines, which results in efficient tunability of the photophysical properties. In particular, isomeric P-chromophores with a protic N–H (indole) are also capable of participating in intramolecular H bonding, offering a new strategy to access a near-infrared chromophore.

Synthesis and Unexpected Optical Properties of Ionic Phosphorus Heterocycles with P-Regulated Noncovalent Interactions

“…Scheme shows the synthetic procedure of new ionic P-heteropines in the current study. Using similar synthetic protocols (method i, ii, iii, and iv) reported in our previous studies, , we were able to synthesize P-heteropines with various [d]-Ar groups, including acenaphthylene (AN), maleimide­(MI), and benzothiadiazole (BTD) (Figure b).…”

“… a Measured in DCM. b Absorption and emission maximum. c Measured by the calibrated integrating sphere. d Measured by a time-correlated single image counting system with DD-375 for excitation and an MCP-PMT detector. e Obtained from ref . f Obtained from ref . g Mono-exponential decay. h Multiple-exponential decay. …”

“…Different from other main-group elements, rich P-chemistry, such as oxidation, alkylation, borylation, metal coordination, etc., promises distinct photophysics of P-OCPs. − Recently, research of P-heteropines started to draw attention in the field of organic functional materials. ,− For example, Hissler and coworkers reported the synthesis of a new series of bithiopene-based phosphepines, which exhibited promising semiconducting characteristics . In another example, we and our collaborators described a new synthetic protocol to synthesize diazaphosphepines with strong electron-accepting characteristics .…”

“…In another example, we and our collaborators described a new synthetic protocol to synthesize diazaphosphepines with strong electron-accepting characteristics . Although the dynamic ground-state structure of the P-heteropines has been well documented in the literature, , the excited-state photophysical characteristics induced by dynamic structures of P-heteropines have been largely overlooked so far . Since the EAIP is hardly applicable to the P-heteropines due to the high-energy barrier of the planarization for the pyramidal P-center, the strategy is limited to fine-tune the excited-state characteristics for the P-heteropines.…”

“…■ RESULTS AND DISCUSSION Synthesis and Characterization of Ionic P-Heteropines. Although several P-heteropines with various πconjugated backbones have reported previously, 26,27,31,40,44 only few ionic P-heteropines with phosphonium cation have been reported in the literature. 42 Scheme 1 shows the synthetic procedure of new ionic P-heteropines in the current study.…”