Microwave-Mediated Synthesis of Bulky Lanthanide Porphyrin–Phthalocyanine Triple-Deckers: Electrochemical and Magnetic Properties

Abstract

Five heteroleptic lanthanide porphyrin-bis-phthalocyanine triple-decker complexes with bulky peripheral groups were prepared via microwave-assisted synthesis and characterized in terms of their spectroscopic, electrochemical, and magnetic properties. These compounds, which were easily obtained under our preparative conditions, would normally not be accessible in large quantities using conventional synthetic methods, as a result of the low yield resulting from steric congestion of bulky groups on the periphery of the phthalocyanine and porphyrin ligands. The electrochemically investigated triple-decker derivatives undergo four reversible one-electron oxidations and three reversible one-electron reductions. The sites of oxidation and reduction were assigned on the basis of redox potentials and UV-vis spectral changes during electron-transfer processes monitored by thin-layer spectroelectrochemistry, in conjunction with assignments of electronic absorption bands of the neutral compounds. Magnetic susceptibility measurements on two derivatives containing Tb and Dy metal ions reveal the presence of ferromagnetic interactions, probably resulting from magnetic dipolar interactions. The Tb derivative shows SMM behavior under an applied field of 0.1 T, where the direct and Orbach process can be determined, resulting in an energy barrier of U = 132.0 K. However, Cole-Cole plots reveal the presence of two relaxation processes, the second of which takes place at higher frequencies, with the data conforming to a 1/t ∝ T relation, thus suggesting that it can be assigned to a Raman process. Attempts were made to form two-dimensional (2D) self-assembled networks on a highly oriented pyrolytic graphite (HOPG) surface but were unsuccessful due to bulky peripheral groups on the two Pc macrocycles.

Electro-activity and magnetic switching in lanthanide-based single-molecule magnets

“…Heteroleptic lanthanide porphyrin (Por)-bisphthalocyanine (L 3 ) triple decker complexes (L 3 )Ln(L 3 )Ln(Por) (Ln = Tb(III) (3) and Dy(III) (4)) were synthesized via microwave-assisted preparation. 24 A complete electrochemical study showed that such complexes highlighted four one-electron oxidations and three one-electron reductions which are centred on the ligands. The oxidation and reduction potentials of the L 3 ligand were identified at 0.50 and −0.65/−1.10 V vs. Fc/Fc + , respectively.…”

“…10). 73 Both coordinated and uncoordinated MeOH molecules can be removed by exposure to air in a single-crystal-to-single-crystal transformation giving the compound (24) (Fig. 10).…”

Magnetic Modification and the Mechanism of Tb‐Phthalocyanine Single Molecule Magnets Prepared by a High Yield Method

“…[5b], Moreover, although the fabrication method of TbPc 2 reported by De Cian et al have been extensively used since 1985, the product yield (around 4 %) is relatively small , . In 2017, Jin and the co‐workers reported an unconventional microwave‐mediated synthesis of bulky Lanthanide porphyrin–Pc triple‐deckers, which can also be used to increase the yield of double‐decker complexes . The impressive study indicates that the search of new synthetic method for SMMs is very valuable.…”

Efficient preparation of 5,10,15,20-tetrakis(4-bromophenyl)porphyrin. Microwave assisted v/s conventional synthetic method, X-ray and hirshfeld surface structural analysis

“…By contrast, variously substituted 5,10,15,20tetraarylporphyrins were shown to be readily accessible in yields up to 43% via microwaveassisted cyclocondensation of different aryl aldehydes with pyrrole, using a minimum amount of propionic acid [18]. Thus, microwave irradiation, also useful in metalloporphyrin synthesis [17,19], appears as a straightforward one-pot practical methodology minimizing reaction time, amount of solvent, and work-up problems.…”