Polymers Based on Benzodipyrrolidone and Naphthodipyrrolidone with Latent Hydrogen-Bonding on the Main Chain

A series of soluble π-conjugated small molecules and polymers containing benzodipyrrolidone (BDP) or naphthodipyrrolidone (NDP) units with latent hydrogen-bonding on the main chain is synthesized and characterized. Spectroscopic study confirms that the tert-butyloxycarbonyl (t-Boc) side unit can be removed by facile thermal annealing treatment, generating the actual hydrogen-bonded compounds. The resulting hydrogen-bonded compounds exhibit distinctly different properties, for instance poorer solubility and smaller bandgap, as compared with their precursors with latent hydrogen-bonding. The single crystal X-ray structure analysis of t-Boc group substituted BDP and NDP indicates that the NDP compounds exhibit better coplanarity and a stronger π–π interaction. The density functional theory computation results of the polymer backbone segments show that the coplanarity of aromatic units is slightly improved. Such a hydrogen-bonding-mediated enhancement of π–π stacking exhibits potential for improving the performance of solution processable organic electronic materials. Hydrogen-bonded polymer P-NDP-FL-2 is an air stable n-type semiconductor with electron mobility 40 times larger than its precursor polymer P-NDP-FL-1 with latent hydrogen-bonding.