PUB - Publikationen an der Universität Bielefeld

The magnetic properties of the bis(phthalocyaninato)terbium complexes [Tb{Pc'(SR)8}2] (1) containing eight beta-positioned long-chain alkylthio substituents SR (a: R=n-C8H17, b: R=n-C12H25) were studied by SQUID measurements, which revealed that both compounds are single-molecule magnets with an effective energy barrier for spin reversal significantly higher than that found for pristine bis(phthalocyaninato)terbium [Tb(Pc)2]. Thin films on gold were fabricated from 1?a and 1?b by chemisorption from solution and were characterised by near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS). In the case of 1?a, atomic force microscopy (AFM) was used in addition. The results are in accord with the formation of self-assembled monolayers which contain the macrocyclic rings mainly in an approximately horizontal orientation. The chemisorption is primarily due to the peripheral SR substituents, giving rise to coordinatively bound thioether units, whose alkyl chains are in an almost parallel orientation with respect to the surface. In the case of 1?b, covalently attached thiolate units were also observed, indicating that the chemisorption process can lead to carbonsulfur bond cleavage. In addition, the crystal structure of 1?a was determined.