New Ethylenedithio-TTF Containing a 2,2,5,5-Tetramethylpyrrolin-1-yloxyl Radical through a Vinylene Spacer and Its FeCl4− Salt—Synthesis, Physical Properties and Crystal Structure Analyses

Kazuki Horikiri,Hideki Fujiwara

doi:10.3390/magnetochemistry3010008

Kazuki Horikiri, Hideki Fujiwara

Open Access

https://doi.org/10.3390/magnetochemistry3010008

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Abstract

To develop novel magnetic conductors exhibiting conducting/magnetic bifunctionalities and peculiar responses to applied magnetic fields, we synthesized new EDT-TTF (ethylenedithiotetrathiafulvalene) donor containing a 2,2,5,5-tetramethylpyrrolin-1-yloxyl radical through a π-conjugated vinylene spacer 1 and examined its electronic and crystal structures, and physical properties. We also prepared its cation radical salts by an electrochemical oxidation method and successfully cleared the crystal structures and magnetic properties of the cation radical salts, 1·FeCl4 and 1·GaCl4. These salts have strongly dimerized one-dimensional arrays of the fully oxidized donor molecules, giving rise to the formation of spin-singlet state of the π cation radical spins in the dimer. On the other hand, the FeCl4- anion locates on the side of the dimers with very short S-Cl contacts and mediates very strong π-d interaction between the donor and anion moieties, resulting in the antiferromagnetic behavior of the Weiss temperature of θ = -3.9 K through its d-π-d interaction.

Highlights

In the field of molecular conductors, much interest has been focused on the development of magnetic conductors, which simultaneously exhibit conducting properties of organic layers of π-electron donors and magnetic properties of inorganic layers of magnetic transition metal anions
The conducting properties of organic layers can be controlled by the application of external magnetic fields and several peculiar physical phenomena such as field-induced superconductivities in the λ- and κ-type BETS salts with FeX4− anions (BETS = bis(ethylenedithio)tetraselenafulvalene; X = Cl and Br) [1,2,3] and anomalies of magnetoresistances corresponding to the spin-flop transitions of magnetic Fe3+ spins [4,5] have been yielded through the π-d interaction between the π-electrons of the organic layers and the magnetic d spins
The studies on molecular conductors using donor molecules substituted with stable organic radicals such as 2,2,6,6-tetramethylpiperidin-1-yloxyl (TEMPO) and nitronyl nitroxide radicals have been performed by several research groups [6,7,8,9] because cation radical salts of such stable radical-containing donors are expected to have strong intramolecular magnetic interactions between their π-cation radical spins and stable radicals and to show outstanding responses to the application of external magnetic fields [10]

Summary

Introduction

In the field of molecular conductors, much interest has been focused on the development of magnetic conductors, which simultaneously exhibit conducting properties of organic layers of π-electron donors and magnetic properties of inorganic layers of magnetic transition metal anions. In such conductors, the conducting properties of organic layers can be controlled by the application of external magnetic fields and several peculiar physical phenomena such as field-induced superconductivities in the λ- and κ-type BETS salts with FeX4− anions (BETS = bis(ethylenedithio)tetraselenafulvalene; X = Cl and Br) [1,2,3] and anomalies of magnetoresistances corresponding to the spin-flop transitions of magnetic Fe3+ spins [4,5] have been yielded through the π-d interaction between the π-electrons of the organic layers and the magnetic d spins. TThheerreeffoorree,, ttoo mmiinniimmiizzee tthhee sstteerriicc bbuullkkiinneessss ooff tthhiiss rardadiciaclapl aprta, rwt,e dweesigdneesdigannedewaethnyelweneedtihtyhlieon-teedtriaththioia-tfeutlrvaatlheinaefu(ElvDaTle-nTeTF()EmDoTl-eTcuTlFe)comnotalienciunlge aco2n,2ta,5in,5i-ntgetraa2m,2e,t5h,5y-ltpeytrrarmoleinth-1y-lyplyorxryollirna-d1i-cyalol xthyrloruagdhicaalπt-hcroonujughgaateπd-cvoinnyjulegnaetesdpvacineyr l1enbeecsapuasceerit1s πbe-ccoanujsuegiattsedπ-hcoexnajutrgiaetneedchheaxinatwrieilnl eencshuarientwheilcl oepnlsaunraeritthyebceotpwleaennartihtye TbeTtFwaenedn stthaeblTeTrFadaincdalsptaabrtlse. Foulertchuelerm1.oFrue,rtwheerwmiollrde,iswcuesws itlhl edidsecutasisl tohfeXd-reatayilsionfgXle-rcaryyssitnagl lsetrcurcytsutarel satnruaclytuseres aanndalmysaegsnaentidc pmroapgenretiteics opfrtohpeeFrteiCesl4o−fatnhdeGFaeCCll44−− asnaldts GofamClo4−lescaulltes 1opfrempoalreecdubley 1anperleepctarroecdhebmyicaanl oelxeicdtartoicohnemmeicthaloodx. iBdeactaiounsemthetehFoedC. lB4e−casaulstecothnetaFienCs lt4h−rseaeltkcinodntsaoinf sspthinres,enkaimndeslyo, fthsepiπn-sc,antiaomnerlayd,itchael sπp-icnastioonf trhaeddicoanl sopripnasrotfs,ththeedsotnaobrlepoarrgtsa,nthicersatdabiclaelosragnadnitchreadFeic3a+lsdasnpdinths,etFhee3+mdasgpnientsi,cthinetemraacgtnioentisc binettewraecetniotnhsesbeestwpienesnatrheeosfessppeicnisalairnetoerfesspt.ecial interest

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