Thermogravimetry (TG) and differential thermal analyses (DTA) of simple and mixed lanthanide complexes have been studied. These studies gave very interesting results and led to the following conclusions:
(1) The presence of water molecules either in a lattice or coordinated was indicated in a thermal study of (a) neodymium barbiturate simple complexes and its oxine mixed complexes, (b) dysprosium dimethyl-glyoximate and diacetylmonoximate, and (c) samarium phenanthroline, N-phenylurea, and N-N' diphenylurea simple complexes.
(2) One could postulate different routes of decomposition. However, on close examination of the results of TG and DTA, only one route of decomposition is possible. Examples of such cases are (a) gadolinium-dimethyl-glyoxime-diphenylthiourea mixed complex and (b) gadolinium thiourea-urea-mixed complex.
(3) Based on a study of thermal analysis, the possible routes of decomposition and formation of intermediates can be postulated. The intermediates formed do sometimes have a definite composition. They can be isolated and their composition established. Sometimes, such intermediates cannot be synthesized by normal methods. Hence, the study of thermal analyses leads to the synthesis of certain complexes that, under normal conditions, are difficult to synthesize. Such an example is the formation of the gadolinium-thiourea simple complex in a thermal study of the mixed complex of Gadolinium-dimethyl-glyoxime-thiourea.
(4) The study of thermal analyses of several simple and mixed lanthanide complexes indicated that certain ligands such as dimethyl-glyoxime, diacetylmonoxime, and thiourea exhibit the same thermal stability in both simple and mixed completes. The thermal stability of the above ligands in simple and mixed lanthanide complexes is discussed.