31519-62-7Relevant articles and documents
Synthesis, characteristics and photoluminescent properties of novel Ir-Eu heteronuclear complexes containing 2-carboxyl-pyrimidine as a bridging ligand
Lian, Ping,Wei, Huibo,Zheng, Chen,Nie, Yifan,Bian, Jiang,Bian, Zuqiang,Huang, Chunhui
, p. 5476 - 5482 (2011)
Two novel iridium(iii) complexes, [Ir(dfppy)2(pmc)] and [Ir(ppy)2(pmc)] (dfppy = 2-(4′,6′-difluoro-phenyl) pyridine, ppy = 1-phenyl-pyridine), were designed and synthesized using 2-carboxyl-pyrimidine (Hpmc) as an ancillary ligand. Single crystals were obtained and characterized by single crystal X-ray diffraction. The tetrametallic complexes {[(CN)2Ir(μ-pmc)]3EuCl 3} (CN = dfppy, ppy) were synthesized using the iridium(iii) complexes as "ligands". Photophysical and theoretical studies indicate that [Ir(dfppy)2(pmc)] is more suitable for sensitizing the emission of Eu(iii) ions than [Ir(ppy)2(pmc)]. The Royal Society of Chemistry.
Tuning spin-crossover transition temperatures in non-symmetrical homoleptic meridional/facial [Fe(didentate)3]2+complexes: what for and who cares about it?
Deorukhkar, Neel,Besnard, Céline,Guénée, Laure,Piguet, Claude
, p. 1206 - 1223 (2021/02/09)
The [FeN6] chromophores found in [Fe(didentate)3]2+complexes, where didentate is a non-symmetrical 2-(6-membered-heterocyclic ring)-benzimidazole ligand (Lk), exist as mixtures of two geometricalmer(C1-symmetry) andfac(C3-symmetry) isomers. Specific alkyl-substituted six-membered heterocyclic rings connected to the benzimidazole unit (pyridines in ligandsL1-L3, pyrazines inL4-L5and pyrimidines inL6-L7) control the ligand field strength and the electron delocalization so that [FeII(Lk)3]2+display tunable thermally-induced spin transitions in solution. Thermodynamic, spectroscopic (UV-Vis, NMR) and magnetic studies in solution demonstrate that [Fe(L6)3]2+(L6= 1-methyl-2-(pyrimidin-2-yl)-1H-benzo[d]imidazole) exhibits a close to room temperature spin transition (T1/2= 273(3) K) combined with a high stability formation constant n acetonitrile), which makes this complex suitable for the potential modulation of lanthanide-based luminescence in polymetallic helicates. A novel method is proposed for assigning specific thermodynamic spin crossover parameters tofac-[Fe(L6)3]2+andmer-[Fe(L6)3]2+isomers in solution. The observed difference relies mainly on the entropic content ΔSmerSCO? ΔSfacSCO= 11(1) J mol?1K?1, which favors the spin transition for the meridional isomer. Intermolecular interactions occurring in the crystalline state largely overcome minor thermodynamic trends operating in diluted solutions and a single configurational isomer is usually observed in the solid state. Among the thirteen solved crystal structures1-13containing the [M(Lk)3]2+cations (M = Fe, Ni, Zn,Lk=L6-L7), pure meridional isomers are observed six times, pure facial isomers also six times and a mixture (44%merand 56%fac) is detected only once. Solid-state magnetic data recorded for the FeIIcomplexes show the operation of slightly cooperative spin transitions in7(fac-[Fe(L6)3]2+) and12(mer-[Fe(L7)3]2+). For the meridional isomer in6, a two-step spin state transition curve, associated with two phase transitions, is detected.
Solvent Polarity Predictably Tunes Spin Crossover T1/2 in Isomeric Iron(II) Pyrimidine Triazoles
Rodríguez-Jiménez, Santiago,Barltrop, Alexis S.,White, Nicholas G.,Feltham, Humphrey L. C.,Brooker, Sally
, p. 6266 - 6282 (2018/06/14)
Two isomeric pyrimidine-based Rdpt-type triazole ligands were made: 4-(4-methylphenyl)-3-(2-pyrimidyl)-5-phenyl-4H-1,2,4-triazole (L2pyrimidine) and 4-(4-methylphenyl)-3-(4-pyrimidyl)-5-phenyl-4H-1,2,4-triazole (L4pyrimidine). 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: [FeII(L2pyrimidine)2(NCS)2] (1), [FeII(L2pyrimidine)2(NCSe)2] (2), 2·1.5H2O, [FeII(L2pyrimidine)2(NCBH3)2]·2CHCl3 (3·2CHCl3), 3 and 3·2H2O, [FeII(L4pyrimidine)2(NCS)2] (4), 4·H2O, [FeII(L4pyrimidine)2(NCSe)2] (5), 5·2CH3OH, 5·1.5H2O, and [FeII(L4pyrimidine)2(NCBH3)2]·2.5H2O (6·2.5H2O). Single-crystal X-ray diffraction reveals that the N6-coordinated iron(II) centers in 1, 2, 3·2CHCl3, 4, 5, and 5·2CH3OH 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 3·2CHCl3, which is low spin (LS). Solid-state magnetic measurements show that only 3·2CHCl3 (T1/2 above 400 K) and 5·1.5H2O (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)2CO, CH3CN, and CH3NO2 solutions for the BH3 analogues 3 and 6 led to a 6:1 ratio of Lnpyrimidine/Fe(II) being employed for the solution studies. These revealed SCO activity in all five solvents, with T1/2 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.
