Synthesis And LB Film Characters Of Novel Side-chain Substituted Rare Earth Phthalocyaninto Complexes

The study of nano-sized supramolecular structures formed by self-organization is of great interest for the development of molecular electronics and ionics devices. In this field, the construction of supramolecular wires and channels capable of transporting electrons is an attractive and challenging direction. Phthalocyanines are an important class of pigments that have been found applications in various disciplines. This series of tetrapyrrole derivatives can form complexes with almost the complete Periodic Table of elements. In particular, sandwich-type complexes of phthalocyanines with large metal ions such as rare earth, actinide, early transition, and main group metals have been obtained. The rare earth sandwich complexes have attracted great attention due to their possible applications in molecular electronics, molecular optronics, and molecular iono-electronics. Among various approaches used to construct supramolecular structures for phthalocyaninato metal complexes, Langmuir-Blodgette techniques have proved versatile. A lot of work has been focused on the formation, structure, and gas-sensing properties of monomeric phthalocyanine derivatives. By contrast, the reports on the sandwich-type phthalocyaninato rare earth complexes have been rather scarce.Recently, we have started to pay attention to the formation characteristics of sandwich tetrapyrrole rare earth complex LB films. The aim of the present paper is not only to add more information on the LB film characteristics of sandwich-type phthalocyaninto rare earth compounds but also to give insight into the influence of the length and number of alkoxy side chains on the pure LB film formation of bis(phthalocyaninato) rare earth compounds. Herein we describe the formation, spectroscopic characterstics, and structure of nano-sized supramolecular structures of a series of alkoxy side-chains substituted sandwich-type phthalocyaninto complexes both Eu[Pc(OC_nH_2n+1)8]₂(n = 4, 5, 6, 7, 8, 12, 16) and EuPc[Pc(OC_nH_2n+1)₈] (n = 4, 8, 12) formed by Langmuir-Blodgette techniques. And influence of the length and number of alkoxy side chains on the self-organization character of phthalocyanine rings was discussed in this paper. Ever since their early synthesis at the beginning of last century, phthalocyanines have been an important class of dyes and pigments. In closely related with their unique spectroscopic and electrochemical properties, they macromolecules have been found important applications in materials science, medicine, optical storage, and photocatalysis. Because of their large conjugated molecular structure together with strongÏ€-Ï€interaction between aromatic rings, phthalocyanine derivatives have also been used as staple building blocks for ordered molecular systems.It is well known that incorporating substituents onto the phthalocyanine ring is the most important method to tune the physi-chemical, electrochemical, and spectroscopic properties of phthalocyanine derivatives. Thus far, various kinds of different substituents such as alkyl, alkoxy, and thioalkyl groups have been introduced onto the peripheral and / or non-peripheral positions of phthalocyanine ligand. However, there still exists no reliable report on octakis(alkoxycarbonyl)phthalocyanine derivatives despite their great potential application in photodynamic therapy (PDT). In 1972, Boston and Bailar claimed without mass spectrum the synthesis of octakis(octacarboxylated)phthalocyanine by tetramerization of 1,2,4,5-tetracyanobenzene or pyromellitic dianhydride, the only evidence being the elemental analysis and IR spectrum. With this octakis(octacarboxylated)phthalocyanine as starting material, further reaction with alcohol through acyl chlorination led to octakis(alkoxycarbonyl)phthalocyanines accordingly, again without elemental analysis and mass spectroscopic evidence.As part of our continuous efforts to develop various new species of phthalocyanine molecular materials, recently we developed an efficient synthetic pathway for preparing 4,5-di(octyloxycarbonyl)phthalonitrile with o-xylene as starting material. With this 4,5-di(octyloxycarbonyl)phthalonitrile available at hand as the best and most common starting material for preparing phthalocyanines, corresponding octakis(octyloxycarbonyl)phthalocyanines have been easily prepared and isolated in good yield.Both electrochemical and theoretical calculation results reveal the electron-withdrawing nature of octyloxycarbonyl groups attached onto the peripheral positions of phthalocyanine ring. It is worth noting that these compounds not only represent the first examples of oktakis(alkoxycarbonyl)phthalocyanine derivatives, but more importantly are good starting materials for preparing water soluble phthalocyanines with great potential applications in PDT.