Characterization of a Robust Co^II Fluorescent Complex Deposited Intact On HOPG

Abstract

The new diimine fluorescent ligand ACRI-1 based on a central acridine yellow core is reported along with its coordination complex [Co2 (ACRI-1)2 ] (1), a fluorescent weak ferromagnet. Due to the strong fluorescence of the acridine yellow fluorophore, it is not completely quenched when the ligand is coordinated to Co(II) . The magnetic properties of bulk complex 1 and its stability in solution have been studied. Complex 1 has been deposited on highly ordered pyrolitic graphite (HOGP) from solution. The thin films prepared have been characterized by AFM, time-of-flight secondary ion mass spectrometry (TOF-SIMS), grazing incidence X-ray diffraction (GIXRD), X-ray absorption spectroscopy (XAS), X-ray magnetic circular dichroism (XMCD) and theoretical calculations. The data show that the complex is robust and remains intact on the surface of graphite.

CoII and CuII Fluorescent Complexes with Acridine‐Based Ligands

“…The dc magnetic susceptibility of complex 1Co shows that it is a ferromagnet with T C = 5 K, as reported in 2014 . We studied the dc magnetic susceptibility of complexes 1Cu , 2Co , 2Cu , 3Co and 3Cu in the 2–300 K temperature range and at applied dc fields of 300 and 5000 Oe.…”

“…As we reported in 2014, the reaction of the ligand ACRI‐1 with a cobalt(II) salt resulted in a precipitate that was recrystallized and characterized as [Co 2 (ACRI‐1) 2 ] ( 1Co ) . In complex 1Co the two cobalt ions are tetracoordinated in a distorted tetrahedral environment.…”

“…However, in these cases the single crystals were destroyed and the chloroform did not replace CH 2 Cl 2 or dmf in the structures. From the data in Table and the packing of complexes 1Cu· 8CHCl 3 , 2Cu· 5CHCl 3 and complex 1Co in CHCl 3 , one can conclude that the packing is dictated by the coordination sphere of the metal, but this is not the only factor. With distorted square‐planar Cu II , 1Cu· 8CHCl 3 forms a porous structure, however, when the methyl groups in ACRI‐1 are removed, as in 2Cu· 5CHCl 3 , or the phenyl groups are replaced by naphthyls, as in 3Cu· 4dmf, the Cu II complexes are not as flat as complex 1Cu (clearly seen in Figure ) and they crystallize in a compact structure similar to that reported for complex 1Co .…”

“…Combining magnetic properties with fluorescence is not straight forward due to the CHEQ effect. However, some coordination complexes with specially designed ligands have been prepared that combine fluorescence ligands and single‐molecule magnet (SMM) properties and others that combine fluorescence and ferromagnetism . In this respect, ligand design is very important to obtain multifunctional, optical and magnetic complexes as the emission properties of the ligand can be easily quenched by metal coordination.…”

“…The relative dispositions of the two binding pockets should result in ferromagnetic coupling between two metals coordinated to one ligand , . We have shown how the ACRI‐1 Co II complex [Co 2 (ACRI‐1) 2 ] ( 1Co ) is a robust fluorescent ferromagnet that can be deposited intact on highly oriented pyrolytic graphite (HOPG) . For the surface deposition, the ligand was designed with aromatic rings that would assist π–π stacking and van der Waals interactions with the graphite surface.…”