Sahadevan Suchithra Ashoka, Abhervé Alexandre, Monni Noemi, Sáenz de Pipaón Cristina, Galán-Mascarós José Ramón, Waerenborgh João C, Vieira Bruno J C, Auban-Senzier Pascale, Pillet Sébastien, Bendeif El-Eulmi, Alemany Pere, Canadell Enric, Mercuri Maria Laura, Avarvari Narcis
Laboratoire MOLTECH-Anjou UMR 6200, UFR Sciences, CNRS , Université d'Angers , Bât. K, 2 Bd. Lavoisier , 49045 Angers , France.
Dipartimento di Scienze Chimiche e Geologiche , Università degli Studi di Cagliari , I-09042 Monserrato (Cagliari) , Italy.
J Am Chem Soc. 2018 Oct 3;140(39):12611-12621. doi: 10.1021/jacs.8b08032. Epub 2018 Sep 24.
The mixed-valence FeFe 2D coordination polymer formulated as [TAG][FeFe(ClCNAn)]·(solvate) 1 (TAG = tris(amino)-guanidinium, ClCNAn = chlorocyanoanilate dianionic ligand) crystallized in the polar trigonal space group P3. In the solid-state structure, determined both at 150 and at 10 K, anionic 2D honeycomb layers [FeFe(ClCNAn)] establish in the ab plane, with an intralayer metal-metal distance of 7.860 Å, alternating with cationic layers of TAG. The similar Fe-O distances suggest electron delocalization and an average oxidation state of +2.5 for each Fe center. The cation imposes its C symmetry to the structure and engages in intermolecular N-H···Cl hydrogen bonding with the ligand. Magnetic susceptibility characterization indicates magnetic ordering below 4 K and the presence of a hysteresis loop at 2 K with a coercive field of 60 Oe. Mössbauer measurements are in agreement with the existence of Fe(+2.5) ions at RT and statistic charge localization at 10 K. The compound shows semiconducting behavior with the in-plane conductivity of 2 × 10 S/cm, 3 orders of magnitude higher than the perpendicular one. A small-polaron hopping model has been applied to a series of oxalate-type FeFe 2D coordination polymers, providing a clear explanation on the much higher conductivity of the anilate-based systems than the oxalate ones.
化学式为[TAG][FeFe(ClCNAn)]·(溶剂化物)1的混合价态FeFe二维配位聚合物（TAG = 三(氨基)胍鎓，ClCNAn = 氯氰基苯胺二价阴离子配体）结晶于极性三方空间群P3中。在150 K和10 K下测定的固态结构中，阴离子二维蜂窝层[FeFe(ClCNAn)]在ab平面中形成，层内金属 - 金属距离为7.860 Å，与TAG阳离子层交替排列。相似的Fe - O距离表明电子离域，且每个Fe中心的平均氧化态为 +2.5。阳离子将其C对称性赋予结构，并与配体形成分子间N - H···Cl氢键。磁化率表征表明在4 K以下存在磁有序，在2 K时存在磁滞回线，矫顽场为60 Oe。穆斯堡尔测量结果与室温下Fe(+2.5)离子的存在以及10 K时的统计电荷局域化一致。该化合物表现出半导体行为，面内电导率为2×10 S/cm，比垂直方向的电导率高3个数量级。一种小极化子跳跃模型已应用于一系列草酸盐型FeFe二维配位聚合物，为苯胺基体系比草酸盐体系具有高得多的电导率提供了清晰的解释。
