Spectroscopic and thermal characterization of tetrathiomolybdate-organic amine homologous systems

The homologous series of organic–inorganic hybrid single crystals (diethylenetriamine-H2-MoS4—I, triethylenetetramineH2-MoS4—II and 1,4-diazobicyclo-2,2,2-octaneH-NH4-MoS4—III) were prepared by passing hydrogen sulfide gas in the aqueous solution of ammonium heptamolybdate and their respective amines. These crystals were analysed using Fourier Transform-Infrared (FT-IR), UV–vis and 1H NMR spectroscopy. The discrepancies in the bond angles and bond lengths have been theoretically explained in terms of hybridisation variations. The thermal analytical techniques such as TG/DTG and DSC were used to study thermal properties at high and low temperatures. DSC at low temperature suggested reversible solid–solid transitions and the respective ΔH, ΔS and ΔG have been derived. SEM analysis of the crystals showed the sedimented smooth layers of these sulfido-metallic crystals before heat treatment were converted into fine powder with tiny capillary pores in the bulk after thermal treatment.