Au@poly(N-propargylamide) Nanoparticles: Preparation and Chiral Recognition

This communication reports the first gold nanoparticles (NPs) chirally functionalized with optically active helical substituted polyacetylene (the resulting hybrid particles are defined as Au@PPA NPs). The novel nanoparticles consist of gold as core and optically active helical poly( N -propargylamide) as shell and show considerable optical activity derived from helical poly( N -propargylamide) chains with predominantly one-handed screw sense. The Au@PPA NPs are prepared by a three-step approach: i) a thiol-containing N -propargylamide monomer [M th , HC≡CCH 2 NHCO(CH 2 ) 10 SH] is synthesized and characterized with FTIR and 1 HNMR spectroscopy and elemental analysis; ii) a copolymer (poly(M th - co -M ch )) was prepared by starting from monomer M th and another chiral N -propargylamide monomer (M ch ); poly(M th - co -M ch ) formed helical conformations and showed optical activities; and, iii) Au@PPA NPs are prepared from hydrogen tetrachloroaurate (III) and poly(M th - co -M ch ) through a one-spot procedure by using LiBH 4 as reducing agent. The as-obtained hybrid nanoparticles are characterized by FTIR spectroscopy, TEM, UV-vis absorption and circular dichroism (CD) techniques. UV-vis and CD measurements demonstrated the remarkable optical activity of the Au@PPA NPs. More interestingly, the Au@PPA NPs show much stronger UV-vis and CD sigals when compared to the corresponding orginal helical copolymer, poly(M th - co -M ch ). The chiral hybrid nanoparticles demonstrate different absorption toward (R)-(+)- and (S)-(−)-1-phenylethylamines, preferentially adsorbing the (S)-isomer.