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Structures of rhenium(I) complexes with 3‐hydroxyflavone and benzhydroxamic acid as O , O ′‐bidentate ligands and confirmation of π‐stacking by solid‐state NMR spectroscopy
Author(s) -
Schutte-Smith Marietjie,
Roodt Andreas,
Alberto Roger,
Twigge Linette,
Visser Hendrik Gideon,
Kirsten Leo,
Koen Renier
Publication year - 2019
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229619002717
Subject(s) - crystallography , denticity , molecule , rhenium , triclinic crystal system , chemistry , orthorhombic crystal system , nuclear magnetic resonance spectroscopy , crystal structure , stereochemistry , stacking , intramolecular force , hydrogen bond , inorganic chemistry , organic chemistry
The synthesis and crystal structures of two new rhenium(I) complexes obtained utilizing benzhydroxamic acid (BHAH) and 3‐hydroxyflavone (2‐phenylchromen‐4‐one, FlavH) as bidentate ligands, namely tetraethylammonium fac ‐(benzhydroxamato‐κ 2 O , O ′)bromidotricarbonylrhenate(I), (C 8 H 20 N)[ReBr(C 7 H 6 NO 2 )(CO) 3 ], 1 , and fac ‐aquatricarbonyl(4‐oxo‐2‐phenylchromen‐3‐olato‐κ 2 O , O ′)rhenium(I)–3‐hydroxyflavone (1/1), [Re(C 15 H 9 O 3 )(CO) 3 (H 2 O)]·C 15 H 10 O 3 , 3 , are reported. Furthermore, the crystal structure of free 3‐hydroxyflavone, C 15 H 10 O 3 , 4 , was redetermined at 100 K in order to compare the packing trends and solid‐state NMR spectroscopy with that of the solvate flavone molecule in 3 . The compounds were characterized in solution by 1 H and 13 C NMR spectroscopy, and in the solid state by 13 C NMR spectroscopy using the cross‐polarization magic angle spinning (CP/MAS) technique. Compounds 1 and 3 both crystallize in the triclinic space group P with one molecule in the asymmetric unit, while 4 crystallizes in the orthorhombic space group P 2 1 2 1 2 1 . Molecules of 1 and 3 generate one‐dimensional chains formed through intermolecular interactions. A comparison of the coordinated 3‐hydroxyflavone ligand with the uncoordinated solvate molecule and free molecule 4 shows that the last two are virtually completely planar due to hydrogen‐bonding interactions, as opposed to the former, which is able to rotate more freely. The differences between the solid‐ and solution‐state 13 C NMR spectra of 3 and 4 are ascribed to inter‐ and intramolecular interactions. The study also investigated the potential labelling of both bidentate ligands with the corresponding fac ‐ 99m Tc‐tricarbonyl synthon. All attempts were unsuccessful and reasons for this are provided.