ROOF-SHAPED HYDROXY HOSTS - SYNTHESIS, COMPLEX-FORMATION AND X-RAY CRYSTAL-STRUCTURES OF INCLUSION-COMPOUNDS WITH ETOH, NITROETHANE AND BENZENE

A series of crystalline host molecules 1 and 2a-e, based on a characte ristic 9,10-dihydro-9,10-ethanoanthracene rigid framework and appended diarylmethanol clathratogenic groups, has been synthesized and studie d with regard to their inclusion behaviour. These hosts form crystalli ne inclusion compounds with a variety of uncharged organic molecules, ranging from protic dipolar to apolar compounds (183 different species ), but show a preference for amines and aromatic hydrocarbons. The bis -methanols are largely superior to the mono-methanols, except for the 4-chlorophenyl substituted methanol, which has proved to have equal ef ficiency. The building principles and the mode of complexation of the host compound 2a 10-dihydro-9,1O-ethanoanthracene-11,12-dimethanol) wi th ethanol (protic), nitroethane (aprotic polar) and benzene (aprotic apolar) as guests have been investigated by single crystal X-ray diffr action. The conformation of the host molecule observed in the 1:2 (hos t:guest) EtOH complex is different from that in the nitroethane (1:1) or benzene (2:1) inclusions. The host-guest contact pattern in 2a . Et OH (1:2) features a huge 16-membered loop of H-bonds involving four fu nctional OH groups of both host and guest, with one intra-host H-bond for each of the two host molecules of the 2:4 (host:guest) aggregate. On the other hand, in the compounds of 2a with the aprotic guest speci es nitroethane and benzene the host hydroxys are involved in specific intramolecular OH...pi-aryl contact, thus yielding true lattice-type i nclusions, although with different organizations. Accordingly, in 2a . nitroethane (1:1) the polar guest units fill up the voids between the bulky host molecules, while in 2a . benzene (2:1) the host molecules are arranged so as to form tunnels in the crystallographic c direction , where the guests are located.