Selective recognition of biogenic amine hydrochlorides by heteroditopic dihomooxacalix[4]arenes

Ion-pair recognition-complexation of monoamine neurotransmitters and trace amine hydrochlorides takes place - with outstanding efficiency and selectivity - within the pi-rich cavity and the pocket formed at the lower rim by the two ureido moieties of the tailor-made dihomooxacalixarene receptors 1 and 2. The solid-state structure of 1 is also reported.