Design, Structural Characterization and Catalytic Activity of Incomplete Dicubane Clusters of N-Substituted Diethanolamines

• Published in: Journal of cluster science 2017-05, Vol.28 (3), p.1355-1377
• Main Authors: Sama, Farasha, Ansari, Istikhar A., Raizada, Mukul, Ahmad, Musheer, Ashafaq, Mo, Shahid, M., Das, Babulal, Shankar, Krapa, Siddiqi, Zafar A.
• Format: Article
• Language: English
• Subjects: Catalysis; Catalytic activity; Chemistry; Chemistry and Materials Science; Clusters; Cobalt; Crystallography; Diethanolamine; Electrons; Ethylbenzene; Inorganic Chemistry; Ligands; Nanochemistry; Nitrates; Original Paper; Oxidation; Physical Chemistry; Radiation; Single crystals; Software; Structural analysis; Supramolecular frameworks; Xylene
• ISSN: 1040-7278; 1572-8862
• DOI: 10.1007/s10876-016-1145-1

A series of four new clusters with cationic unit [Co 4 (µ 3 -OH)(Rdea) 2 (L–L) 4 ] 4+ [R = –CH 3 ( 1 and 2 ) or –CH 2 CH 2 CH 2 CH 3 ( 3 and 4 ), L–L = 1,10-phenanthroline or 2,2′-bipyridine] is designed and characterized by elemental, spectroscopic (FTIR, ESI MS, UV–visible), thermal, electrochemical, magnetic, SEM, EDX, PXRD and single crystal X-ray crystallographic techniques. Spectral and single crystal X-ray studies reveal the complexes 1 – 4 are tetranuclear clusters where the primary aminoalcohol derivative ligand is present in dianionic form i.e., Medea 2− or n Budea 2− . It is confirmed from the magnetic and bond valence summation data that the four cobalt ions are present in mixed valent states (Co 2 2+ –Co 2 3+ ), which is further corroborated from the Co–O and Co–N bond lengths in X-ray structure. The bridging two hydroxide ions consolidate the tetranuclear clusters by bonding with three neighboring metal ions and a rare incomplete dicubane core is formed in all the complexes. A supramolecular framework is generated by H-bonding, π–π, CH···π, and H···H interactions. Presence of N -alkyl group and N -heterocyclic chelator facilitates the generation of these non covalent interactions thus stabilizing the framework. Of all the complexes reported here, 1 is found most efficient catalyst for the cobalt-catalyzed aerobic oxidation of neat ethylbenzene and p -xylene.