Functionalized fluorescent terephthalate monomers and their attempted polyester formation

Yvonne S L Choo,José Antonio,Marta Giamberini,Paul G Waddell,Andrew C Benniston

doi:10.1039/d0ob01533d

Abstract

The reaction of diethyl 2,5-bis(tert-butyl)phenoxy-3,6-dihydroxyterephthalate (1) with tetraethylene glycol di(p-toluenesulfonate) under high-dilution conditions afforded several isolated products. Two products were identified as macrocycles with one being the 1 + 1 crown ether derivative 3 (10% yield), and the second being the 2 + 2 crown ether compound D3 (19% yield). The X-ray structure for 3 was determined with the asymmetric unit observed to comprise half of the molecule. The small crown ether ring of 3 interacts with K+ or H+ ions in MeOH, but binding is weak and the macrocyclic cavity is too small to fully encapsulate the K+ ion. Transesterification of compounds 1, its methylated version 2 and 3 with diols such as ethylene glycol or 1,4-butandiol produced monomers (M1-M3) which were reacted with terephthaloyl chloride. Short oligomers were produced (PolyM1-PolyM3) rather than extensive polymeric materials and all displayed solid state fluorescence. The absorption and fluorescence properties of M1-M2 and their polymers can be related to subtle structural changes. The Stokes shift for M2 of 15 627 cm-1 in DCM is one of the largest observed for a simple organic chromophore in fluid solution.

Highlights

Terephthalate derivatives are the cornerstone of the manufacture of the widely used polyester plastics,[1] which have found numerous commercial applications in areas such as bottles, packaging, cosmetics, thermal insulating materials and car accessories, to name but a few
Synthesis and structure The synthetic procedure used in the production of the crown ether is illustrated in Scheme 1 starting from the precursor 1 prepared previously using published methods.[16]
To minimise polymerisation reactions, the high dilution method was used in which the diol 1 and the tetraethylene glycol di( p-toluenesulfonate) were added slowly to a refluxing MeCN solution

Summary

Introduction

Terephthalate derivatives are the cornerstone of the manufacture of the widely used polyester plastics,[1] which have found numerous commercial applications in areas such as bottles, packaging, cosmetics, thermal insulating materials and car accessories, to name but a few. Using the molecular geometry of the crystal structure as the starting point an energy minimisation calculation was performed using DFT (B3LYP) and a 6-311G basis set.

Results

Conclusion