Termohromno ponašanje halogenidnih kompleksa kobalta(II) u višekomponentnim sistemima

Abstract

U ovoj doktorskoj disertaciji proučavano je građenje i termohromno ponašanje hloro kompleksa kobalt(II) jona u tri različita medijuma: amonijum-nitrat + zformamid (z= 2, 3, 4, 5, 6 i 20), amonijum-nitrat + zN-metilformamid (z = 3, 4, 5, 6 i 20) i amonijum-nitrat + zN,N-dimetilformamid (z = 3) u temperaturnom intervalu od 308,15 do 348,15 K. Cilj ovog istraživanja je bio određivanje stabilnosti termohromnih kompleksa kobalta(II) koji se grade sahloridnim i nitratnim jonima i molekulima rastvarača, pronalaženje kvalitativne i kvantitativne zavisnosti konstanti stabilnosti kompleksa kobalta(II) od temperature i molskog odnosa komponenti ispitivanih sistema. Termodinamički parametri, koji karakterišu reakcije asocijacije u ispitivanim sistemima izračunati su na osnovu dobijenih konstanti stabilnosti na različitim temperaturama. Drugi deo ovog rada obuhvata fizičko-hemijsku karakterizaciju ispitivanih sistema, i to: merenje gustine, provodljivosti i njihove viskoznosti. Na osnovu dobijenih podataka razmotrene su vrste interakcija koje se javljaju među česticama rastvarača i rastvorene supstance, kao i njihov uticaj na građenje kompleksnih čestica kobalta(II). Ispitivani sistemi su posebno interesantni, jer predstavljaju dobre medijume za ispitivanje termohromizma u praksi.

In this thesis absorption spectra of cobalt(II) chloride in three ammonium nitrate binary mixtures with organic solvents (formamide, N-methylformamide and N,N-dimethylformamide) at different temperatures (from 308.15 to 248.15 K) and compositions have been investigated in the wavelength range 400-800 nm. Influence of the temperature and composition of the mixture on complex formation between cobalt(II) and nitrate ions, chloride ions and/or solvent molecules have been studied. Thermodynamic parameters for cobalt(II)-ligand association in different solventswere also determined. The second part of this work involves physical-chemical characterization of the studied systems, namely: density, electrical conductivity and viscosity measurements. On the basis of the obtained data, the types and nature of the solute-solvent interactions that occur, as well as their impact on the cobalt(II) complex formation were discussed. In all investigated systems, complexes of cobalt(II) change the geometry and colour from pale pink to dark blueupon addition of chloride ions and upon heating/cooling. Hence, additional chemical energy can be stored in such system. Because the effective working temperatures match very well with that readily achievable under sunlight, these thermochromic systems present an example of novel materials suitable for auto-regulated protection and energy storage.