5-[4-(N-叔丁基-N-氨氧基)苯基]嘧啶的Co3(RL)2(hfac)6梯形配合物

Co3(RL)2(hfac)6 ladder complex of 5-[4-(N-tert-butyl-N-aminoxyl)phenyl]pyrimidine.

作者信息

Field Lora M, Morón M Carmen, Lahti Paul M, Palacio Fernando, Paduan-Filho Armando, Oliveira Nei F

机构信息

Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, USA.

出版信息

Inorg Chem. 2006 Mar 20;45(6):2562-7. doi: 10.1021/ic051884w.

DOI:10.1021/ic051884w

PMID:16529477

Abstract

5-[4-(N-tert-butyl-N-aminoxyl)phenyl]pyridimine (4NITPhPyrim = RL) forms a 1-D ladder polymer complex with Co(hfac)2 of stoichiometry Co3(RL)2(hfac)6, having antiparallel [Co(II)RL]n linear chains (rails) that are cross-linked by Pyrim-Co(hfac)2-Pyrim rungs. The magnetic behavior above 100 K is consistent with contributions from one high-spin Co(II) ion (the cross-link, S = 3/2) plus two Co-ON units with strongly antiferromagnetic (AFM) metal-radical exchange (each S = 1). The chiT data show an AFM downturn as the temperature drops. Assuming weak exchange along chain portions of the polymer due to poor spin polarization across the phenyl-pyrimidine bond in RL, a linear three-spin (S = 1, 3/2, and 1) fit to the T > 18 K data yields an AFM cross-linker (rung) effective exchange of J(CL)/k = (-)5.3 K = (-)3.7 cm(-)(1). Superexchange (sigma-orbital overlap) is a likely mechanism for the effective AFM exchange between CoON and Co spin sites in the three-spin groupings.

摘要

5-[4-(N-叔丁基-N-氨氧基)苯基]嘧啶（4NITPhPyrim = RL）与Co(hfac)₂形成化学计量比为Co₃(RL)₂(hfac)₆的一维阶梯聚合物配合物，具有反平行的[Co(II)RL]ₙ线性链（轨道），这些链通过嘧啶-Co(hfac)₂-嘧啶梯级交联。100 K以上的磁行为与一个高自旋Co(II)离子（交联部分，S = 3/2）加上两个具有强反铁磁（AFM）金属-自由基交换的Co-ON单元（每个S = 1）的贡献一致。χT数据显示随着温度降低出现AFM下降。假设由于RL中苯基-嘧啶键上的自旋极化不佳，聚合物链部分的交换较弱，对T > 18 K数据进行线性三自旋（S = 1、3/2和1）拟合，得到AFM交联剂（梯级）的有效交换为J(CL)/k = (-)5.3 K = (-)3.7 cm⁻¹。超交换（σ轨道重叠）可能是三自旋组合中CoON和Co自旋位点之间有效AFM交换的机制。