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Solvent Polarity Predictably Tunes Spin Crossover T-1/2 in Isomeric Iron(II) Pyrimidine Triazoles

Rodríguez-Jimenez, Santiago; Barltrop, Alexis S.; White, Nicholas; Feltham, Humphrey L.; Brooker, Sally

Description

Two isomeric pyrimidine-based Rdpt-type triazole ligands were made: 4-(4-methylphenyl)-3-(2-pyrimidyl)-5-phenyl-4 H-1,2,4-triazole (L-2pyrimidine) and 4-(4-methylphenyl)-3-(4-pyrimidyl)-5-phenyl-4 H-1,2,4-triazole (L-4pyrimidine). When reacted with [FeII(pyridine)(4)(NCE)2], where E = S, Se, or BH3, two families of mononuclear iron(II) complexes are obtained, including six solvatomorphs, giving a total of 12 compounds: [Fe-II(L-2pyrimidine)(2)(NCS)2] (1), [Fe-II(L-2pyrimidine)(2)(NCSe)(2)] (2),...[Show more]

dc.contributor.authorRodríguez-Jimenez, Santiago
dc.contributor.authorBarltrop, Alexis S.
dc.contributor.authorWhite, Nicholas
dc.contributor.authorFeltham, Humphrey L.
dc.contributor.authorBrooker, Sally
dc.date.accessioned2019-11-21T01:24:24Z
dc.identifier.issn0020-1669
dc.identifier.urihttp://hdl.handle.net/1885/186447
dc.description.abstractTwo isomeric pyrimidine-based Rdpt-type triazole ligands were made: 4-(4-methylphenyl)-3-(2-pyrimidyl)-5-phenyl-4 H-1,2,4-triazole (L-2pyrimidine) and 4-(4-methylphenyl)-3-(4-pyrimidyl)-5-phenyl-4 H-1,2,4-triazole (L-4pyrimidine). When reacted with [FeII(pyridine)(4)(NCE)2], where E = S, Se, or BH3, two families of mononuclear iron(II) complexes are obtained, including six solvatomorphs, giving a total of 12 compounds: [Fe-II(L-2pyrimidine)(2)(NCS)2] (1), [Fe-II(L-2pyrimidine)(2)(NCSe)(2)] (2), 2 1.5H(2)O, [Fe-II(L-2pyrimidine)(2)(NCBH3)(2)]2CHCl3 (32CHCl3), 3 and 32H(2)O, [Fe-II(L-4pyrimidine)(2)(NCS)2] (4), 4H(2)O, [Fe-II(L-4pyrimidine)(2)(NCSe)(2)] (5), 52CH(3)OH, 51.5H(2)O, and [Fe-II(L-4pyrimidine)(2)(NCBH3)(2)] 2.5H(2)O (6 2.5H(2)O). Single-crystal X-ray diffraction reveals that the N-6-coordinated iron(II) centers in 1, 2, 3 2CHCl(3), 4, 5, and 52CH(3)OH have two bidentate triazole ligands equatorially bound and two axial NCE co-ligands trans-coordinated. All structures are high spin (HS) at 100 K, except 3 2CHCl(3), which is low spin (LS). Solid-state magnetic measurements show that only 3 2CHCl(3) ( T1/2 above 400 K) and 5 1.5H(2)O ( T1/2 = 110 K) undergo spin crossover (SCO); the others remain HS at 300-50 K. When 3 2CHCl3 is heated at 400 K it desorbs CHCl3 becoming 3, which remains HS at 400-50 K. UV-Vis studies in CH2Cl2, CHCl3, (CH3)(2)CO, CH3CN, and CH3NO2 solutions for the BH3 analogues 3 and 6 led to a 6:1 ratio of L (npyrimidine)/Fe(II) being employed for the solution studies. These revealed SCO activity in all five solvents, with T-1/2 values for the 2-pyrimidine complex (247-396 K) that were consistently higher than for the 4-pyrimidine complex (216-367 K), regardless of solvent choice, consistent with the 2-pyrimidine ring providing a stronger ligand field than the 4-pyrimidine ring. Strong correlations of solvent polarity index with the T1/2 values in those solvents are observed for each complex, enabling predictable T1/2 tuning by up to 150 K. While this correlation is tantalizing, here it may also be reflecting solvent-dependent speciation-so future tests of this concept should employ more stable complexes. Differences between solid-state (ligand field; crystal packing; solvent content) and solution (ligand field; solvation; speciation) effects on SCO are highlighted.
dc.format.mimetypeapplication/pdf
dc.language.isoen_AU
dc.publisherAmerican Chemical Society
dc.rights© 2018 American Chemical Society
dc.sourceInorganic Chemistry
dc.titleSolvent Polarity Predictably Tunes Spin Crossover T-1/2 in Isomeric Iron(II) Pyrimidine Triazoles
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume57
dc.date.issued2018-01-14
local.identifier.absfor030207 - Transition Metal Chemistry
local.identifier.ariespublicationu4485658xPUB1912
local.publisher.urlhttps://pubs.acs.org
local.type.statusPublished Version
local.contributor.affiliationRodríguez-Jimenez, Santiago, University of Otago
local.contributor.affiliationBarltrop, Alexis S., University of Otago
local.contributor.affiliationWhite, Nicholas, Research School of Chemistry, ANU
local.contributor.affiliationFeltham, Humphrey L., University of Otago
local.contributor.affiliationBrooker, Sally, University of Otago
local.description.embargo2037-12-31
local.bibliographicCitation.issue11
local.bibliographicCitation.startpage6266
local.bibliographicCitation.lastpage6282
local.identifier.doi10.1021/acs.inorgchem.8b00128
local.identifier.absseo970103 - Expanding Knowledge in the Chemical Sciences
dc.date.updated2019-05-12T08:20:06Z
local.identifier.thomsonID000434491700013
CollectionsANU Research Publications

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