ELSEVIER Supramoleculur Science 4 ( I 997) 41742 I 4’ 1997 Elsevier Science Ltd Printed in Great Britain. All rights reserved PII: SO968-5677(97)00024-2 0968-5677/97/$17.00 Resorcinol calixarenes (resorcarenes): Langmuir- Blodgett films and optical properties 0. Omar, A. K. Ray* and A. K. Hassan Physical Electronics and Fibre-optics Laboratories, School of Engineering, Sheffield Hal/am University, Pond Street, Sheffield Sl 1WB, UK and F. Davis Department of Chemistry, Sheffield University, Brook Hill, Sheffield S3 7HF, UK (Received 6 September 1996; revised 6 December 1996) Specially synthesized amphiphilic resorcinol calixarene (resorcarene 2) molecules have been deposited as Langmuir-Blodgett (LB) films on a variety of substrates including hydrophobically treated glass slides, silicon and gold-coated glass slides. A value of 1.9nm2 is obtained for the area per molecule from measurements of pressure/area isotherms of the floating layer. Optical absorption studies within the ultraviolet-visible frequency region have been performed on these molecules in both LB films and in solution of resorcarene 2 in chloroform, containing 10% ethanol. Molecular aggregation in the form of dimerization is believed to take place during film formation. Further analysis has been carried out for Langmuir-Blodgett films of resorcarene 2 by using Fourier transform infra-red spectroscopy, low-angle X-ray diffraction and surface plasmon resonance (SPR) techniques. The monolayer thickness of 1.6nm found from SPR measurements is consistent with that from other experimental observations. 0 1997 Elsevier Science Ltd. All rights reserved. (Keywords:calixanene; Langmul-Blodgett films; optical characterization) INTRODUCTION Calixarenes and resorcarenes are known as molecular baskets owing to their ability to form complexes with a range of chemical species’. These compounds form a series of well-defined cyclic oligomers, allowing variations of the cavity size according to the requirements of different guest molecules. Films of p-tert-butyl calixarene molecules adhere well to the gate oxide layer of a field-effect transistor for application as a chemical sensor in liquid media2. Substituted resorcin[4]arenes can be deposited in the form of a self-assembled monolayer on a quartz crysta13. Calixarenes were shown to form stable monolayers when spread over a water subphase and their films deposited by the Langmuir- Blodgett (LB) technique are quite homogeneous4. Such films have great potential for chemical sensing applications, where they are capable of complexing with neutral compounds such as aromatic compounds and hydrocarbons5. Where carboxyl and amino groups have been included into the calix(8)arene rings two materials have been produced *To whom correspondence should be addressed whose alternate-layer LB films have displayed a pyroelectric effect6. Highly ordered structures have also been produced by immobilizing resorcarenes in gold-thiol monolayers, a technique known as self- assembly film deposition7. Resorcarenes have also been reported to rapidly form a multilayered structure from a bulk solution onto such an ordered film by van der Waals’ interdigitation-hydrogen- bonding alternations*. This paper reports the results of optical characterization of the azobenzene derivative, resorcarene 2 molecules. These molecules have been deposited as LB films on a variety of solid substrates. The LB technique allows the layer-by-layer transfer of molecules from the subphase onto a solid substrate, enabling an ordered molecular structure to be obtained. Optical methods include Fourier transform infra-red spectroscopy (FTIR) and surface plasmon resonance (SPR). SPR is a very sensitive optical probe of the optical properties of metal surfaces. The technique can be used to determine the optical parameters of thin dielectric layers such as LB films deposited on a metal surface’. It has been widely exploited as an optical technique for chemical and bio sensing. SUPRAMOLECULAR SCIENCE Volume 4 Numbers 3-4 1997 417