NMR study of phthalide-type poly(phenylene)s. Symmetry and additivity.

All H and C NMR signals of the four poly(phenylenephthalides): polydiphenylenephthalide (P(DPh)-1), polyterphenylenephthalide (P(TPh)-2) and two sequentially ordered polymers with different ratios of alternating diphenylenephthalide and terphenylenephthalide units (P(DTPh)-3, P(DDTPh)-4) were assigned unequivocally with two-dimensional NMR techniques ( H- H COSY and NOESY; H- C HSQC and HMBC). There are four types of polyphenylene fragments: not symmetrical end, symmetrical inner, symmetrical pre-end and formally symmetric pre-end. The equivalent carbon atoms in these fragments have different chemical shifts. A full additivity of the chemical shifts for the side phthalide and polyphenylene carbon atoms was revealed. A new structure of diads with a mirror symmetry plane, passing through the middle of aromatic moieties, is proposed. Copyright © 2017 John Wiley & Sons, Ltd.