Molecule of the Month

Phthalocyanine

Discovery and History

The word phthalocyanine - from the Greek for naphtha (rock oil) and cyanine (blue) was first used by Linstead in 1933 to describe a new class of organic compounds. Phthalocyanine itself was probably discovered by accident in 1907, as a by-product during the synthesis of o-cyanobenzamide, but it was not until almost 20 years later that a patent was filed describing a manufacturing process. The extensive chemical studies by Linstead et al were followed by structural studies by J Monteath Robertson at the Royal Institution and Glasgow - the first crystal structures of relatively large organic molecules. Studies of semiconductivity and gas adsorption effects followed soon after in Nottingham.

Lead Phthalocyanine
Click for 3D structure

Properties and Uses

Phthalocyanine has been widely exploited in industry and academia, in a variety of applications ranging from conventional dye stuffs to catalysis, coatings for read/write CD-ROM's and as an anti-cancer agent. The majority of applications use the metal-substituted form of the molecule - a process which has been applied to every group in the periodic table - for example the Royal Mint use the popular copper-substituted variety as a blue dye in 5 pound notes.

Rewriteable Optical Media

This is an increasingly important topic in the information storage industry - read/write cd-rom technology at low cost has obvious implications for the computer, education and communications industries.

Chemical Sensors

Many types of chemical sensor based on phthalocyanines have been proposed - including thin film resistive devices, FET sensors and Langmuir-Blodgett films.

Oncology

The fluoraluminium phthalocyanine has been extensively studied for potential use as a target molecule in anti-cancer treatment.
Alan Wilson February 1996.