TY - JOUR
T1 - Giant heterometallic [Mn 36 Ni 4 ] 0/2 - and [Mn 32 Co 8 ] "loops-of-loops-and-supertetrahedra" molecular aggregates
AU - Charalambous, Maria
AU - Moushi, Eleni E.
AU - Nguyen, Tu N.
AU - Papatriantafyllopoulou, Constantina
AU - Nastopoulos, Vassilios
AU - Christou, George
AU - Tasiopoulos, Anastasios J.
N1 - Publisher Copyright:
© 2019 Charalambous, Moushi, Nguyen, Papatriantafyllopoulou, Nastopoulos, Christou and Tasiopoulos.
PY - 2019
Y1 - 2019
N2 - We report the synthesis, crystal structures and magnetic properties of the giant heterometallic [Mn 36 Ni 4 ] 2-/0 (compounds 1, 2)/[Mn 32 Co 8 ] (compound 3) "loops-of-loops-and-supertetrahedra" molecular aggregates and of a [Mn 2 Ni 6 ] 2+ compound (cation of 4) that is structurally related with the cation co-crystallizing with the anion of 1. In particular, after the initial preparation and characterization of compound [Mn 2 Ni 6 (μ 4 -O) 2 (μ 3 -OH) 3 (μ 3 -Cl) 3 (O 2 CCH 3 ) 6 (py) 8 ] 2+ [Mn 36 Ni 4 (μ 4 -O) 8 (μ 3 -O) 4 (μ 3 -Cl) 8 Cl 4 (O 2 CCH 3 ) 26 (pd) 24 (py) 4 ] 2- (1) we targeted the isolation of (i) both the cationic and the anionic aggregates of 1 in a discrete form and (ii) the Mn/Co analog of [Mn 36 Ni 4 ] 2- aggregate. Our synthetic efforts toward these directions afforded the discrete [Mn 36 Ni 4 ] "loops-of-loops-and-supertetrahedra" aggregate [Mn 36 Ni 4 (μ 4 -O) 8 (μ 3 -O) 4 (μ 3 -Cl) 8 Cl 2 (O 2 CCH 3 ) 26 (pd) 24 (py) 4 (H 2 O) 2 ] (2), the heterometallic Mn/Co analog [Mn 32 Co 8 (μ 4 -O) 8 (μ 3 -O) 4 (μ 3 -Cl) 8 C l2 (μ 2 -OCH 2 CH 3 ) 2 (O 2 CCH 3 ) 28 (pd) 22 (py) 6 ] (3) and the discrete [Mn 2 Ni 6 ] 2+ cation [Mn 2 Ni 6 (μ 4 -O) 2 (μ 3 -OH) 4 (μ 3 -Cl) 2 (O 2 CCH 3 ) 6 (py) 8 ](ClO 4 )(OH) (4). The structure of 1 consists of a mixed valence [Mn28IIIMn8IINi4II] 2- molecular aggregate that contains two Mn8IIINi2II loops separated by two Mn6IIIMn4II supertetrahedral units and a [Mn2IIINi6II] 2+ cation based on two [Mn III Ni3II(μ 4 -O)(μ 3 -OH) 1.5 (μ 3 -Cl) 1.5 ] 4+ cubane sub-units connected through both mono- and tri-atomic bridges provided by the μ 4 -O 2- and carboxylate anions. The structures of 2-4 are related to those of the compounds co-crystallized in 1 exhibiting however some differences that shall be discussed in detail in the manuscript. Magnetism studies revealed the presence of dominant ferromagnetic interactions in 1-3 that lead to large ground state spin (ST) values for the "loops-of-loops-and-supertetrahedra" aggregates and antiferromagnetic exchange interactions in 4 that lead to a low (and possibly zero) ST value. In particular, dc and ac magnetic susceptibility studies revealed that the discrete [Mn 36 Ni 4 ] aggregate exhibits a large ST value ~ 26 but is not a new SMM. The ac magnetic susceptibility studies of the [Mn 32 Co 8 ] 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 2+ ions and a resulting out-of-phase ac signal whose peak is at very low T.
AB - We report the synthesis, crystal structures and magnetic properties of the giant heterometallic [Mn 36 Ni 4 ] 2-/0 (compounds 1, 2)/[Mn 32 Co 8 ] (compound 3) "loops-of-loops-and-supertetrahedra" molecular aggregates and of a [Mn 2 Ni 6 ] 2+ compound (cation of 4) that is structurally related with the cation co-crystallizing with the anion of 1. In particular, after the initial preparation and characterization of compound [Mn 2 Ni 6 (μ 4 -O) 2 (μ 3 -OH) 3 (μ 3 -Cl) 3 (O 2 CCH 3 ) 6 (py) 8 ] 2+ [Mn 36 Ni 4 (μ 4 -O) 8 (μ 3 -O) 4 (μ 3 -Cl) 8 Cl 4 (O 2 CCH 3 ) 26 (pd) 24 (py) 4 ] 2- (1) we targeted the isolation of (i) both the cationic and the anionic aggregates of 1 in a discrete form and (ii) the Mn/Co analog of [Mn 36 Ni 4 ] 2- aggregate. Our synthetic efforts toward these directions afforded the discrete [Mn 36 Ni 4 ] "loops-of-loops-and-supertetrahedra" aggregate [Mn 36 Ni 4 (μ 4 -O) 8 (μ 3 -O) 4 (μ 3 -Cl) 8 Cl 2 (O 2 CCH 3 ) 26 (pd) 24 (py) 4 (H 2 O) 2 ] (2), the heterometallic Mn/Co analog [Mn 32 Co 8 (μ 4 -O) 8 (μ 3 -O) 4 (μ 3 -Cl) 8 C l2 (μ 2 -OCH 2 CH 3 ) 2 (O 2 CCH 3 ) 28 (pd) 22 (py) 6 ] (3) and the discrete [Mn 2 Ni 6 ] 2+ cation [Mn 2 Ni 6 (μ 4 -O) 2 (μ 3 -OH) 4 (μ 3 -Cl) 2 (O 2 CCH 3 ) 6 (py) 8 ](ClO 4 )(OH) (4). The structure of 1 consists of a mixed valence [Mn28IIIMn8IINi4II] 2- molecular aggregate that contains two Mn8IIINi2II loops separated by two Mn6IIIMn4II supertetrahedral units and a [Mn2IIINi6II] 2+ cation based on two [Mn III Ni3II(μ 4 -O)(μ 3 -OH) 1.5 (μ 3 -Cl) 1.5 ] 4+ cubane sub-units connected through both mono- and tri-atomic bridges provided by the μ 4 -O 2- and carboxylate anions. The structures of 2-4 are related to those of the compounds co-crystallized in 1 exhibiting however some differences that shall be discussed in detail in the manuscript. Magnetism studies revealed the presence of dominant ferromagnetic interactions in 1-3 that lead to large ground state spin (ST) values for the "loops-of-loops-and-supertetrahedra" aggregates and antiferromagnetic exchange interactions in 4 that lead to a low (and possibly zero) ST value. In particular, dc and ac magnetic susceptibility studies revealed that the discrete [Mn 36 Ni 4 ] aggregate exhibits a large ST value ~ 26 but is not a new SMM. The ac magnetic susceptibility studies of the [Mn 32 Co 8 ] 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 2+ ions and a resulting out-of-phase ac signal whose peak is at very low T.
KW - Crystal structures
KW - Diols
KW - Heterometallic clusters
KW - Magnetic properties
KW - Mn
UR - http://www.scopus.com/inward/record.url?scp=85064630461&partnerID=8YFLogxK
U2 - 10.3389/fchem.2019.00096
DO - 10.3389/fchem.2019.00096
M3 - Article
SN - 2296-2646
VL - 7
JO - Frontiers in Chemistry
JF - Frontiers in Chemistry
IS - MAR
M1 - 96
ER -