The Relationship between Structure and Properties in ZnII Complexes of Bulky N,N′-Diarylformamidinate N-Oxides

• Published in: European journal of inorganic chemistry Vol. 2016; no. 1; pp. 177 - 185
• Main Authors: Cibian, Mihaela, Langis-Barsetti, Sophie, Ferreira, Janaina G., Hanan, Garry S.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.01.2016; WILEY‐VCH Verlag; Wiley; Wiley Subscription Services, Inc
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Density functional calculations; Electrons; N,O ligands; O ligands; Physical Sciences; Science & Technology; Structure elucidation; Substituent effects; Zinc; OXIDATION; MOLECULAR-STRUCTURE; ZN(II); STEREOCHEMISTRY; Substituent effects; CRYSTAL-STRUCTURES; Density functional calculations; Zinc; N; ZINC(II) COMPLEXES; EXCITATION-ENERGIES; ELECTROLUMINESCENT PROPERTIES; METAL; Structure elucidation; O ligands; ELECTRONIC STATES
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201501106

Homoleptic zinc(II) complexes (3a–3d) of the bulky N,N′‐diarylformamidinate N‐oxide ligands N‐hydroxy‐N,N′‐bis(2,6‐diisopropylphenyl)formamidine (2a), N‐hydroxy‐N,N′‐bis(2,6‐dimethylphenyl)formamidine (2b), N‐hydroxy‐N,N′‐bis(2‐isopropylphenyl)formamidine (2c) and N‐hydroxy‐N,N′‐bis(2‐biphenyl)formamidine (2d) were synthesized and characterized. Their solid‐state structures are presented together with their solution properties, as examined by NMR and UV/Vis spectroscopy, and cyclic voltammetry. Theoretical calculations [DFT and time‐dependent DFT (TD‐DFT)] were performed to assess and to rationalize the influence of ligand modification on the properties of the complexes: the highest occupied molecular orbital (HOMO), localized on the NCNO moiety, is less influenced by the substitution pattern, whereas the lowest unoccupied molecular orbital (LUMO), localized on the aryl ring with the O–N moiety, is directly affected; therefore, the optical band gap can be fine‐tuned for potential applications. In the zinc(II) bis(chelates) of bulky N,N′‐diarylformamidinate N‐oxide ligands, the highest occupied molecular orbital (HOMO) is localized on the N=C–N–O moiety and, hence, less influenced by the substitution pattern, whereas the lowest unoccupied molecular orbital (LUMO), localized on the aryl ring with the O–N moiety, is directly affected, and the HOMO–LUMO band gap can be fine‐tuned.