1D Copper(II)-Aroylhydrazone Coordination Polymers: Magnetic Properties and Microwave Assisted Oxidation of a Secondary Alcohol

Manas Sutradhar; Elisabete C B A Alegria; Tannistha Roy Barman; M Fátima C Guedes da Silva; Cai-Ming Liu; Armando J L Pombeiro

doi:10.3389/fchem.2020.00157

1D Copper(II)-Aroylhydrazone Coordination Polymers: Magnetic Properties and Microwave Assisted Oxidation of a Secondary Alcohol

Front Chem. 2020 Mar 6:8:157. doi: 10.3389/fchem.2020.00157. eCollection 2020.

Authors

Manas Sutradhar¹, Elisabete C B A Alegria^{1

2}, Tannistha Roy Barman¹, M Fátima C Guedes da Silva¹, Cai-Ming Liu³, Armando J L Pombeiro¹

Affiliations

¹ Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.
² Área Departamental de Engenharia Química, Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, Lisbon, Portugal.
³ National Laboratory for Molecular Sciences, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.

Abstract

The 1D Cu(II) coordination polymers [Cu₃(L¹)(NO₃)₄(H₂O)₂]_n (1) and [Cu₂(H₂L²)(NO₃)(H₂O)₂]_n(NO₃)_n (2) have been synthesized using the aroylhyrazone Schiff bases N' ¹,N' ²-bis(pyridin-2-ylmethylene)oxalohydrazide (H₂L¹) and N' ¹,N' ³-bis(2-hydroxybenzylidene)malonohydrazide (H₄L²), respectively. They have been characterized by elemental analysis, infrared (IR) spectroscopy, UV-Vis spectroscopy, electrospray ionization mass spectrometry (ESI-MS), single crystal X-ray diffraction and variable temperature magnetic susceptibility measurements (for 2). The ligand (L¹)^2- coordinates in the iminol form in 1, whereas the amide coordination is observed for (H₂L²)^2- in 2. Either the ligand bridge or the nitrate bridge in 2 mediates weak antiferromagnetic coupling. The catalytic performance of 1 and 2 has been investigated toward the solvent-free microwave-assisted oxidation of a secondary alcohol (1-phenylethanol used as model substrate). At 120°C and in the presence of the nitroxyl radical 2,2,6,6-tetramethylpiperydil-1-oxyl (TEMPO), the complete conversion of 1-phenylethanol into acetophenone occurs with TOFs up to 1,200 h^-1.

Keywords: Cu(II) complexes; X-ray structure; coordination polymer; magnetism; microwave assisted oxidation of alcohols.