Synthetic ability of dinuclear mesocates containing 1, 3-bis(diazinecarboxamide)benzene bridging ligands to form complexes of increased nuclearity. Crystal structures, magnetic properties and theoretical studies. Issue 31 (28th July 2017)

• Record Type: Journal Article
• Authors: Palacios, Maria A.; Morlieras, Jessica; Herrera, Juan Manuel; Mota, Antonio J.; Brechin, Euan K.; Triki, Smail; Colacio, Enrique
• Is Part Of: Dalton transactions. Volume 46:Issue 31(2017)
• Page Start: 10469
• Page End: 10483
• Publication Date: 2017-07-28
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c7dt02288c
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Dinuclear complexes can be used as building blocks to afford unusual heteronuclear species of different topology. Abstract : Triple stranded NiII2-metallacyclic complexes Na2.5 [Ni2 (bpcb)3 ]·0.5OH·18.5H2 O (1 ) and Na2 [Ni2 (bpzcb)3 ]·16H2 O (2 ), and double stranded CuII2-metallacyclic complexes [Cu2 (bpcb)2 (H2 O)2 ]·8H2 O (3 ) and [Cu2 (bpzcb)2 (H2 O)2 ]·4H2 O (4 ) have been assembled from the tailored bisbidentate bridging ligands, 1, 3-bis(pyrimidine-2-carboxamide)benzene (H2 bpcb) and 1, 3-bis(pyrazine-2-carboxamide)benzene (H2 bpzcb), and the corresponding nitrate salts of the metal ions. Following the "complex as ligand" strategy, 1 can be assembled with either Ni 2+, Co 2+ ions or the [Mn(acen)Cl] complex to afford unique, neutral, bent trinuclear molecules [M II NiII2(bpcb)3 ]· x H2 O (5 and6 ) and the 2D honeycomb-like complex (PPh4 ){[Ni2 (bpcb)3 ]2 [Mn(acen)]3 } (7 ), respectively. In these cases, the Ni2 units are linked to the corresponding metal ions through amidate oxygen atoms and the outward nitrogen atom of one of the pyrimidine rings of the bcpb ligand. The assembly of2 with Ln 3+ ions (Ln 3+ = Tb, Gd) leads to one dimensional complexes of formula [{[Ni2 (bpzcb)3 ]Tb(H2 O)5 }(CF3 SO3 )·THF·5H2 O] n (8 ) and [{[Ni2 (bpzcb)3 ]Ln(H2 O)4 (NO3 )}·2THF· n H2 O] n (9 and10 ) (Ln 3+ = Gd and Tb), where the dinuclear Ni2 units are joined to two Ln 3+ ions exclusively through amidate oxygen atoms of two different ligands. The analyses of the magnetic data indicate that1–4 exhibit intradinuclear ferromagnetic interactions between the metal ions through a spin polarisation mechanism, as supported by DFT calculations. Trinuclear complexes5 and6 show predominant antiferromagnetic coupling, which is a result of an antiferromagnetic interaction between one of the Ni 2+ ions of the Ni2 unit and the M 2+ ion through the pyrimidine bridging fragment that is stronger than the polarised ferromagnetic interaction between the Ni 2+ ions through the bpcb ligand in the dinuclear [Ni2 (bpcb)3 ] 2− moiety. Complex7 shows a dominant antiferromagnetic interaction between the Ni 2+ and Mn 2+, whereas the Ni2 Ln (Ln 3+ = Gd, Tb) chain complexes present ferromagnetic interactions inside the Ni2 mesocate unit as well as between the Ni 2+ ions of the Ni2 unit and the Ln 3+ ions. The magnetic exchange interactions in these new materials have been experimentally analysed and supported by theoretical DFT studies.