Palacios Maria A, Morlieras Jessica, Herrera Juan Manuel, Mota Antonio J, Brechin Euan K, Triki Smail, Colacio Enrique
Departamento de Química Inorgánica, Universidad de Granada, Av. Fuentenueva S/N, 18071 Granada, Spain.
Dalton Trans. 2017 Aug 8;46(31):10469-10483. doi: 10.1039/c7dt02288c.
Triple stranded Ni-metallacyclic complexes Na[Ni(bpcb)]·0.5OH·18.5HO (1) and Na[Ni(bpzcb)]·16HO (2), and double stranded Cu-metallacyclic complexes [Cu(bpcb)(HO)]·8HO (3) and [Cu(bpzcb)(HO)]·4HO (4) have been assembled from the tailored bisbidentate bridging ligands, 1,3-bis(pyrimidine-2-carboxamide)benzene (Hbpcb) and 1,3-bis(pyrazine-2-carboxamide)benzene (Hbpzcb), and the corresponding nitrate salts of the metal ions. Following the "complex as ligand" strategy, 1 can be assembled with either Ni, Co ions or the [Mn(acen)Cl] complex to afford unique, neutral, bent trinuclear molecules [MNi(bpcb)]·xHO (5 and 6) and the 2D honeycomb-like complex (PPh){[Ni(bpcb)][Mn(acen)]} (7), respectively. In these cases, the Ni 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 of 2 with Ln ions (Ln = Tb, Gd) leads to one dimensional complexes of formula [{[Ni(bpzcb)]Tb(HO)}(CFSO)·THF·5HO] (8) and [{[Ni(bpzcb)]Ln(HO)(NO)}·2THF·nHO] (9 and 10) (Ln = Gd and Tb), where the dinuclear Ni units are joined to two Ln ions exclusively through amidate oxygen atoms of two different ligands. The analyses of the magnetic data indicate that 1-4 exhibit intradinuclear ferromagnetic interactions between the metal ions through a spin polarisation mechanism, as supported by DFT calculations. Trinuclear complexes 5 and 6 show predominant antiferromagnetic coupling, which is a result of an antiferromagnetic interaction between one of the Ni ions of the Ni unit and the M ion through the pyrimidine bridging fragment that is stronger than the polarised ferromagnetic interaction between the Ni ions through the bpcb ligand in the dinuclear [Ni(bpcb)] moiety. Complex 7 shows a dominant antiferromagnetic interaction between the Ni and Mn, whereas the NiLn (Ln = Gd, Tb) chain complexes present ferromagnetic interactions inside the Ni mesocate unit as well as between the Ni ions of the Ni unit and the Ln ions. The magnetic exchange interactions in these new materials have been experimentally analysed and supported by theoretical DFT studies.
三链镍金属环配合物Na[Ni(bpcb)]·0.5OH·18.5H₂O (1)和Na[Ni(bpzcb)]·16H₂O (2)，以及双链铜金属环配合物[Cu(bpcb)(H₂O)]·8H₂O (3)和[Cu(bpzcb)(H₂O)]·4H₂O (4)，是由定制的双齿桥联配体1,3-双(嘧啶-2-甲酰胺)苯(Hbpcb)和1,3-双(吡嗪-2-甲酰胺)苯(Hbpzcb)与金属离子的相应硝酸盐组装而成。按照“配合物作为配体”的策略，1可以与Ni、Co离子或[Mn(acen)Cl]配合物组装，分别得到独特的中性弯曲三核分子[MNi(bpcb)]·xH₂O (5和6)以及二维蜂窝状配合物(PPh₄){[Ni(bpcb)][Mn(acen)]} (7)。在这些情况下，Ni单元通过酰胺氧原子和bpcb配体中一个嘧啶环的向外氮原子与相应的金属离子相连。2与Ln离子(Ln = Tb, Gd)的组装导致了化学式为[{[Ni(bpzcb)]Tb(H₂O)₉}(CF₃SO₃)·THF·5H₂O] (8)和[{[Ni(bpzcb)]Ln(H₂O)₉(NO₃)}·2THF·nH₂O] (9和10) (Ln = Gd和Tb)的一维配合物，其中双核Ni单元仅通过两个不同配体的酰胺氧原子与两个Ln离子相连。磁性数据分析表明，1 - 4通过自旋极化机制在金属离子之间表现出核内铁磁相互作用，这得到了密度泛函理论(DFT)计算的支持。三核配合物5和6显示出主要的反铁磁耦合，这是由于Ni单元中的一个Ni离子与M离子通过嘧啶桥片段的反铁磁相互作用比双核[Ni(bpcb)]部分中Ni离子通过bpcb配体的极化铁磁相互作用更强的结果。配合物7显示出Ni和Mn之间占主导的反铁磁相互作用，而NiLn (Ln = Gd, Tb)链状配合物在Ni介孔单元内部以及Ni单元的Ni离子与Ln离子之间呈现铁磁相互作用。这些新材料中的磁交换相互作用已经通过实验分析，并得到了理论DFT研究的支持。
