Abstract
A series of five new mononuclear pentagonal bipyramidal Co(II) complexes with the equatorial 2,6-diacetylpyridine bis(semicarbazone) ligand (H2dapsc) and various axial pseudohalide ligands (SCN, SeCN, N(CN)2, C(CN)3, and N3) was prepared and structurally characterizated: [Co(H2dapsc)(SCN)2]∙0.5C2H5OH (1), [Co(H2dapsc)(SeCN)2]∙0.5C2H5OH (2), [Co(H2dapsc)(N(CN)2)2]∙2H2O (3), [Co(H2dapsc)(C(CN)3)(H2O)](NO3)∙1.16H2O (4), and {[Co(H2dapsc)(H2O)(N3)][Co(H2dapsc)(N3)2]}N3∙4H2O (5). The combined analyses of the experimental DC and AC magnetic data of the complexes (1–5) and two other earlier described those of this family [Co(H2dapsc)(H2O)2)](NO3)2∙2H2O (6) and [Co(H2dapsc)(Cl)(H2O)]Cl∙2H2O (7), their theoretical description and the ab initio CASSCF/NEVPT2 calculations reveal large easy-plane magnetic anisotropies for all complexes (D = + 35 − 40 cm−1). All complexes under consideration demonstrate slow magnetic relaxation with dominant Raman and direct spin–phonon processes at static magnetic field and so they belong to the class of field-induced single-ion magnets (SIMs).
Highlights
Large uniaxial magnetic anisotropy has a crucial role in the enhancement of the blocking temperature of magnetization reversal in single molecular magnets (SMMs) [1,2,3,4]
These complexes reveal the rare occurrence of pentagonal bipyramidal stereochemistry about a central metal ion, which results from pentacoordination of the nearly planar H2dapsc (N3OMa2gn)e,toachnemdisttryw20o19l, a5,bx iFlOeRaPEpEiRcRaElVlIEigWands (H2O and/or Cl, NO3, and others) perp2 oefn16dicular to the equatorial pewnithagothneplapenneta[d2e6nt–a3te0].SAchlitffh-boauseghHth2deapcsoc mlpiglaenxdes (oHf2dHap2sdcap=sc a2,n6-ddiaitcsetaylnpyarliodginue es have long been known,btihs(esesmtuicdarybaozfonthe)e, Firigmuraeg1)naentdicitps arnoaploegrutieessar[e1o7f,1co9n–s2id1e,r3a1bl–e3in4t]eraenstd
We present the synthesis and crystal structures of the five new seven-coordination
Summary
Large uniaxial magnetic anisotropy has a crucial role in the enhancement of the blocking temperature of magnetization reversal in single molecular magnets (SMMs) [1,2,3,4]. The experimental and theoretical studies of stable seven-coordinated metal centers with pentagonal bipyramidal geometry showed that such centers are highly promising as anisotropic spin carriers [16,17,18,19,20,21,22,23,24,25]. In this context, 3d-metallocomplexes with the pentadentate Schiff-base H2dapsc ligand (H2dapsc = 2,6-diacetylpyridine bis(semicarbazone), Figure 1) and its analogues are of considerable interest. Luis, and co-worktmehraesgonrgyeatiszvhaeotiuotlnhdienneothtxepaplllraoewsneantctheieoonfSsIMtoafticbthemheaagvpnioreret,icstefhineelscdee(sCooo-fc(IatIlh)leecdofifmieepldllde-xi-neidsnudscheudowcSeIMdsloss)w.lRourweisla,mxLautaiisog,nnaneodftic relaxation for Kramer iocon-ws,orskuercshgaavseCthoe(eIxIp),lawnaititohn pofrethveapirleisnegnceeaosf yth-epfliaelnd-einmduacegdnselotwic maanginseotitcroreplayxa[ti3o9n]f.orThe origin of this large nonK-ruamneiar xioinasl, saunchisaostCroo(pIIy), wisitdh upreevtaoiltinhgeemasyi-xpilnange omfagthneetigc raoniusontrdopeyle[3c9t]r. oThneicorsigtainteofwthiisth the excited electronic staletaleergcsterbonenoicnca-suutnastiaeesxiobaeflcasanpuissieonto-rfoosprpybiniist-odcrbuoieut ctpooultiphnleignm.g.ixing of the ground electronic state with the excited
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