Remarkable effect of alkynyl substituents on the fluorescence properties of a BN-phenanthrene.

Alberto Abengózar,Juan J Vaquero,Patricia García-García,David Sucunza

doi:10.3762/bjoc.15.122

Abstract

A series of BN-phenanthrenes with substituents of a diverse nature have been synthesized by palladium-catalyzed cross-coupling reactions of a common chloro-substituted precursor, which was made from readily available materials in only four steps. Evaluation of the photophysical properties of the prepared compounds unveiled an impressive effect of the presence of alkynyl substituents on the fluorescence quantum yield, which improved from 0.01 in the parent compound to up to 0.65 in derivatives containing a triple bond.

Highlights

BN-polycyclic aromatic hydrocarbons (BN-PAHs) have received increasing interest over the past few years [1,2,3,4,5], in the field of materials science [6]
We have recently described a methodology for the synthesis of a chloro-substituted BN-benzo[c]phenanthrene and its subsequent derivatization via palladium-catalyzed cross-coupling reactions [30], and we envisioned that this reaction could be used to prepare C7 substituted BN-phenanthrenes (Figure 1)
Once we had developed a useful method for the synthesis of the functionalized BN-phenanthrenes 1, we focussed on our initial goal of evaluating the influence of different substituents on the photophysical properties thereof

Summary

Introduction

BN-polycyclic aromatic hydrocarbons (BN-PAHs) have received increasing interest over the past few years [1,2,3,4,5], in the field of materials science [6]. The presence of aryl or amino substituents at C1, which can be introduced via bromination and subsequent palladium-catalyzed cross coupling, does not have a significant impact on the fluorescence of these compounds (Figure 1) [23]. We were interested in the effect of alkynyl substituents, as their presence in PAHs is known to alter the fluorescence properties thereof markedly [27,28,29].

Results

Conclusion