Journal of Inclusion Phenomena and Macrocyclic Chemistry 34: 235–243, 1999. © 1999 Kluwer Academic Publishers. Printed in the Netherlands. 235 Guest–Host Interactions in Hofmann-T d -type Aniline Clathrates: IR Spectral Study R. MURUGESAN ⋆ School of Chemistry, Madurai Kamaraj University, Madurai - 625 021, India. A. THAMARAICHELVAN Department of Chemistry, Thiagarajar College, Madurai - 625 009, India. P. SAMI ⋆⋆ Department of Chemistry, VHNSN College, Virudhunagar – 626 001, India (Received 18 March 1998; in final form: 7 August 1998) Abstract. Synthesis and IR spectra of novel Hofmann-T d -type aniline clathrates, M(NH 3 ) 2 Zn(CN) 4 ·2C 6 H 5 NH 2 (M = Zn or Cd) are reported for the first time. All the vibrational modes of aniline are characterised. The shifts in ν a (NH 2 ) and ν s (NH 2 ) reveal hydrogen bonding between the NH 2 group of aniline and the cyanide group of the host lattice to be stronger than in Hofmann-type aniline clathrates. However, the out of plane deformation mode of aniline indicates absence of hydrogen bonding between ammonia and the π -cloud of the aniline ring. The related aniline clathrates with bridging Cd(CN) 4 , M(NH 3 ) 2 Cd(CN) 4 ·2C 6 H 5 NH 2 (M=Zn or Cd), exhibit similar behaviour. Key words: inclusion compounds, Hofmann-T d -type clathrates, IR study, guest–host interactions, hydrogen bonding 1. Introduction Inclusion compounds are formed by host lattices with voids or tunnels in which guest molecules are enclathrated. Although organic compounds are well known to show inclusion behaviour, only a very few inorganic complexes exhibit such a property, notable examples being the Hofmann-type and related clathrates which originate from the ammine- or amine-metal(II)-tetracyanometallate(II) host struc- tures [1]. Studies on guest–host interactions in inclusion compounds are of current interest due to the importance of these compounds in molecular recognition, sep- aration of isomers and synthesis of asymmetric and polymeric compounds [1–3]. Guest–host interactions in these clathrates provide an explanation for the effects of enclathration on the structural and spectroscopic properties of both the guest and the host molecules. Despite being weak in nature, these interactions produce ⋆ Author for correspondence. ⋆⋆ Present address: Department of Chemistry, Dr. Sivanthi Aditanar College of Engineering, Tiruchendur-628 217, India.