Universal Interaction of Thermodynamical and Structural Characteristics in Molecular Crystals of Metal β-Diketonates

Abstract

In this paper we are observing the behavior of low-temperature heat capacity for metal β-diketonates to detect the relation between thermodynamic and structural characteristics of these metals. As a starting point, a correlation between the heat capacity and the molecule's effective size was detected for metal tris-βdiketonates:

Crystal structures of chloro-, bromo-, and nitro-substituted chromium(III) acetylacetonates

“…Cr(acacCl) 3 crystallizes through two crystallographically independent molecules, which differs by bond lengths, valence angles and bend of the cycles. Similar packing was identified for Ir(acacCl) 3[5]. Molecules, forming the crystallographic pair, are optical isomers.…”

“…Earlier the bend in chelate metallocycles was reported [10,22]. Such peculiarities are also present in Ir(acacCl) 3 , investigated earlier [5]. Two molecules, forming a crystallographic pair, match each other by mean bond length and differ by bending angle of chelate rings: there are highly bended in one molecule, while flat in the other.…”

“…However, unlike the chromium complex, only two molecules interact in Ir(acacCl) 3 rather than a chain. The most significant difference in structure of 1 and iridium [5] chloroacetylacetonate is C-C bond length in β-methyl groups. C-C bond length of twelve methyl groups in two crystallographically independent molecules significantly differs (by 0.152 Å), reaching 1.631 Å, considerably higher than unsubstituted chelate (1.502 Å [23], mean magnitude).…”

“…For example, structural data were used to calculate thermodynamic characteristics [5]. Possibility of acetylacetonate application is connected with the presence of different functional groups in its *Corresponding author.…”

Error or exemption to the rule? Development of a diagnostic check for thermochemistry of metal–organic compounds

“…The adaptation of the algorithm is based on the reliable C p;m ðcrÞ value for Fe(acac) 3 measured by AC. 55 At the rst step of the GA parametrization we have suggested to dene the Fe(acac) 3 -moiety as a single increment, keeping the general denition of groups attached to the ligand (e.g. increments CH 3 , CF 3 , C 6 H 5 , etc.)…”