ABAB-type phthalocyanines simultaneously bearing electron donating and electron accepting groups. Synthesis, spectroscopy, and structure

Abstract

The ABAB-type 1,4,15,18-tetrapentyloxy-8,11,22,25-tetrachlorophthalocyaninato magnesium compound Mg(trans-TPTCPc) (1) was successfully isolated from the mixed cyclic tetramerization of 4,7-bis(pentyloxy)-1,3-diiminoisoindoline as precursor A, actually the 1,3-diiminoisoindoline form of 3,6-bis(pentyloxy)-1,2-benzenedinitrile, and 4,5-dichlorophthalonitrile as precursor B in refluxing pentanol in the presence of magnesium pentoxide in a relatively good yield of 6.2%. Its molecular structure was clearly revealed on the basis of single crystal X-ray diffraction analysis, representing the first structurally characterized ABAB-type phthalocyanine compound, simultaneously bearing electron-donating pentyloxy groups and electron-accepting chloro substituents. Nevertheless, with 1 as the starting material, the corresponding sandwich-type bis(phthalocyaninato) lutetium double-decker complex Lu^III(trans-TPTCPc)₂ (2) was also prepared and structurally characterized, showing a high hyperpolarizability of 1240 × 10⁻³⁰ esu as determined by harmonic light scattering (HLS), indicating the great potential of these kinds of phthalocyanine compounds in the field of second-order NLO materials.

Our cooperation with Prof. Isabelle Ledoux-Rak started with our acquaintance with her remarkable publications in the area of molecular and materials for photonic applications, especially multifunctional nanoscale compounds and structures combining NLO and laser properties. The USTB group has long been focused on the synthesis and functionality of tetrapyrrole compounds with their nonlinear optical properties also as one of the areas of interest. However, related research has been retarded due to lack of corresponding research methods to perform physical measurements. Fortunately, Prof. Isabelle Ledoux-Rak kindly offered her help to perform the HLS measurements of our samples, which resulted in the present paper being published in Inorg. Chem. Front. With this as a good starting point, we are able to reasonably to look forward to having more fruitful results on the basis of the cooperation between these two groups.