Giant Heterometallic [Mn 36 Ni 4 ] 0/2- and [Mn 32 Co 8 ] "Loops-of-Loops-and-Supertetrahedra" Molecular Aggregates

• Published in: Frontiers in chemistry Vol. 7; p. 96
• Main Authors: Charalambous, Maria, Moushi, Eleni E, Nguyen, Tu N, Papatriantafyllopoulou, Constantina, Nastopoulos, Vassilios, Christou, George, Tasiopoulos, Anastasios J
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 05.03.2019
• Subjects: Chemistry; crystal structures; diols; heterometallic clusters; magnetic properties; Mn; diols; magnetic properties; crystal structures; heterometallic clusters
• ISSN: 2296-2646; 2296-2646
• DOI: 10.3389/fchem.2019.00096

We report the synthesis, crystal structures and magnetic properties of the giant heterometallic [Mn Ni ] (compounds , )/[Mn Co ] (compound ) "loops-of-loops-and-supertetrahedra" molecular aggregates and of a [Mn Ni ] compound (cation of ) that is structurally related with the cation co-crystallizing with the anion of . In particular, after the initial preparation and characterization of compound [Mn Ni (μ -O) (μ -OH) (μ -Cl) (O CCH ) (py) ] [Mn Ni (μ -O) (μ -O) (μ -Cl) Cl (O CCH ) (pd) (py) ] ( ) we targeted the isolation of (i) both the cationic and the anionic aggregates of in a discrete form and (ii) the Mn/Co analog of [Mn Ni ] aggregate. Our synthetic efforts toward these directions afforded the discrete [Mn Ni ] "loops-of-loops-and-supertetrahedra" aggregate [Mn Ni (μ -O) (μ -O) (μ -Cl) Cl (O CCH ) (pd) (py) (H O) ] ( ), the heterometallic Mn/Co analog [Mn Co (μ -O) (μ -O) (μ -Cl) Cl (μ -OCH CH ) (O CCH ) (pd) (py) ] ( ) and the discrete [Mn Ni ] cation [Mn Ni (μ -O) (μ -OH) (μ -Cl) (O CCH ) (py) ](ClO )(OH) ( ). The structure of consists of a mixed valence [ ] molecular aggregate that contains two loops separated by two supertetrahedral units and a [ ] cation based on two [Mn (μ -O)(μ -OH) (μ -Cl) ] cubane sub-units connected through both mono- and tri-atomic bridges provided by the μ -O and carboxylate anions. The structures of - are related to those of the compounds co-crystallized in exhibiting however some differences that shall be discussed in detail in the manuscript. Magnetism studies revealed the presence of dominant ferromagnetic interactions in - that lead to large ground state spin (S ) values for the "loops-of-loops-and-supertetrahedra" aggregates and antiferromagnetic exchange interactions in that lead to a low (and possibly zero) S value. In particular, dc and ac magnetic susceptibility studies revealed that the discrete [Mn Ni ] aggregate exhibits a large S value ~ 26 but is not a new SMM. The ac magnetic susceptibility studies of the [Mn Co ] analog revealed an extremely weak beginning of an out-of-phase tail indicating the presence of a very small relaxation barrier assignable to the anisotropic Co ions and a resulting out-of-phase ac signal whose peak is at very low T.