Influence of long-chain aliphatic dopants on the spectroscopic properties of polyketimine containing 3,8-diamino-6-phenylphenanthridine and ethylene linkage in the main chain. Noncovalent interaction: Proton transfer, hydrogen and halogen bonding

The spectroscopic properties of the aromatic polyketimine containing 3,8-diamino-6-phenylphenanthridine and ethylene linkage in the main chain (PK1) before and after doping are dominated by an interplay of electron-donating and electron-withdrawing effects mediated by its nitrogen atom and active groups in the dopants, respectively. Hydrogen and halogen bond formation or molecular recognition between PK1 and decanoic acid (DCA), n-decyl alcohol (DA), 1,10-dibromodecane (DBr), and n-decyl sulfonic acid (DSA) was investigated in comparison with undoped PK1. UV - vis and Fourier transform infrared (FTIR) absorption, wide-angle X-ray diffraction (WAXD), and the atomic force microscopy (AFM) technique are used to probe the spectroscopic properties of the phenanthridine "core" of PK1 as well as its complexes. Spectral changes were observed for the PK1 after doping, which supported the ionic, hydrogen, and halogen bond formation between the PK1 and protonation agents (dopants). This specific interaction of the dopant with the host polymer influences the polyketimine properties, and the following changes were observed: (i) changes in the band gap (E) of the protonated polyketimine, (ii) changes in the FTIR spectra of doped PK1, (iii) changes in optical micrographs of the protonated PK1 (detected by the AFM technique), and (iv) changes in crystalline structure of doped PK1. Our study demonstrates how the properties of conjugated PK1 can be tuned by the supramolecular engineering concepts, which could be important for optoelectronic applications of the materials. © 2008 American Chemical Society.