Studies on Transition Metal Murexide Complexes

Murexide, a reddish purple compound has the structure shown in Fig. 1. It has received much interest because of its application in chemical analysis and spectrophotometric fields [1, 2]. It is considered as the ammonium salt of purpuric acid and named as ammonium 2,6-dioxo-5-(2,4,6-trioxo-tetrahydro-pyrimidine-5-ylidene amino)-1,2,3,6-tetrahydro-pyrimidine-4-olate. It serves as a metal ion indicator, commonly used in conventional EDTA titrations. It is also used as a chromogenic reagent for conventional spectrophotometric determination of some metals [2]. This indicator has a low potential in the literature and few studies such as surface properties [1], stability constants of its complexes [3, 4] and complex formation kinetics [5] were examined. No physico-chemical properties as well as proposed structures for these complexes were carried out. So, this paper is intended to give spotlight on the structure and thermal properties of some transition metal-murexide complexes. Transition metal complexes are of special interest in industry, medicine and biology and have many applications in thermochromism, antioxidation, vulcanization acceleration, protecting paintings, catalysis and anti-bacteriology. So far, solid-state reactions such as thermal isomerization, conformational changes, polymorphic transformations, thermal phase transitions and thermochromism have a scientific impact for coordination compounds. Our research group has reported a series of articles concerning with the thermal properties of different transition metal complexes with pyrimidine, purine, azo, nitroso, azo-nitroso and amino alcohol derivatives [6–20]. In a continuation of such work the subject of this article is introduced.