DFT calculations as a powerful technique to probe the crystal structure of Al(acac)₃

Abstract

(27)Al, (17)O and (13)C chemical shieldings of aluminum acetylacetonate complex, Al(acac)(3), were calculated at some Density Functional Theory (DFT) levels of theory. In these calculations the X-ray structures of its different polymorphs were used. Using these calculated data observed discrepancies between the X-ray crystallography and solid state NMR experiment were explained in terms of the quality of the NMR data. In this survey we resorted to the simulated spectra using our calculated chemical shifts. In order to confirm our conclusions, electric field gradient (EFG) tensors of the (27)Al and (17)O nuclei were calculated at the same levels of theory as used in the chemical shielding calculations. On the other hand, these calculated chemical shifts and nuclear quadrupole coupling constants (NQCCs) made a correlation between X-ray crystallography and solid state NMR experiments.

Errors in the Calculation of 27Al Nuclear Magnetic Resonance Chemical Shifts

“…For example, Tossell [4] calculated the chemical shieldings of 27 Al, along with other nuclei, by applying the gauge-including atomic orbital (GIAO) method [5,6] with the Hartree-Fock (HF) theory and to elucidate the species formed during the hydrolysis and the oligomerization process of Al(III) in aqueous solution. Amini et al [7,8] applied the HF theory and density functional theory (DFT) to calculate the solid-state 27 Al NMR spectra of aluminum acetylacetonate and other similar complexes for the clarification of the crystal structure of the compounds. Mirzaei et al [9,10] used DFT calculations to calculate 27 Al and 31 P chemical shieldings in the investigation of aluminum phosphide and nitride nanotubes.…”

In Situ Studies on Phase Transitions of Tris(acetylacetonato)-Aluminum(III) Al(acac)3

“…Al(acac) 3 , also known as aluminum acetylacetonate, occurs as various polymorphs: the thermodynamically stable α-phase [33], the γ-polymorph [34] or the δ-phase (observed at 110 K, superstructure of the α-polymorph) [35]. In several publications, the structures of the polymorphs and their properties were reported, e.g., the synthesis and crystal structure [36], Density Functional Theory (DFT) calculations to probe the crystal structure of the polymorphs [37], crystal structure and luminescence [38], thermal cell-expansion (under light irradiation) [39], luminescence of Al(acac) 3 :Cr 3+ [40], thermodynamics of sublimation of Al(acac) 3 [41], just to name a few. The huge number of papers is due to possible applications, i.e., Al(acac) 3 is a common precursor for the preparation of alumina Al 2 O 3 , [36,[42][43][44] for thin films via CVD [45,46] or nanoparticles [42] and several polymers, e.g., polycarbosilanes (PACS) [47,48].…”