scholarly journals Spin-Crossover in Iron(II) Complexes of N,N′-Disubstituted 2,6-Bis(Pyrazol-3-yl)Pyridines: An Effect of a Distal Substituent in the 2,6-Dibromophenyl Group

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 922
Author(s):  
Igor A. Nikovskiy ◽  
Alexander V. Polezhaev ◽  
Valentin V. Novikov ◽  
Dmitry Yu. Aleshin ◽  
Rinat R. Aysin ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Spin Crossover ◽  
Molecular Design ◽  
Variable Temperature ◽  
Bromine Atom ◽  
X Ray Diffraction ◽  
Methyl Group ◽  
X Ray ◽  
Active Iron ◽  
Switchable Materials

A series of new bis(pyrazol-3-yl)pyridines (LR) N,N′-disubstituted by 4-functionalized 2,6-dibromophenyl groups have been synthesized to study the effect of a distal substituent on the spin-crossover (SCO) behaviour of the iron(II) complexes [Fe(LR)2](ClO4)2 by variable-temperature magnetometry, NMR spectroscopy, and X-ray diffraction. The SCO-assisting tendency of the substituents with different electronic and steric properties (i.e., the bromine atom and the methyl group) in the para-position of the 2,6-dibromophenyl group is discussed. Together with earlier reported SCO-active iron(II) complexes with N,N′-disubstituted bis(pyrazol-3-yl)pyridines, these new complexes open the way for this family of SCO compounds to emerge as an effective ‘tool’ in revealing structure–function relations, a prerequisite for successful molecular design of switchable materials for future breakthrough applications in sensing, switching, and memory devices.

scholarly journals Spin State Behavior of A Spin-Crossover Iron(II) Complex with N,N′-Disubstituted 2,6-bis(pyrazol-3-yl)pyridine: A Combined Study by X-ray Diffraction and NMR Spectroscopy

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 793
Author(s):  
Elizaveta K. Melnikova ◽  
Dmitry Yu. Aleshin ◽  
Igor A. Nikovskiy ◽  
Gleb L. Denisov ◽  
Yulia V. Nelyubina
Keyword(s):  
Nmr Spectroscopy ◽  
Spin State ◽  
Metal Ion ◽  
Spin Crossover ◽  
Molecular Design ◽  
Chemical Shifts ◽  
Variable Temperature ◽  
High Spin State ◽  
X Ray Diffraction ◽  
X Ray

A series of three different solvatomorphs of a new iron(II) complex with N,N′-disubstituted 2,6-bis(pyrazol-3-yl)pyridine, including those with the same lattice solvent, has been identified by X-ray diffraction under the same crystallization conditions with the metal ion trapped in the different spin states. A thermally induced switching between them, however, occurs in a solution, as unambiguously confirmed by the Evans technique and an analysis of paramagnetic chemical shifts, both based on variable-temperature NMR spectroscopy. The observed stabilization of the high-spin state by an electron-donating substituent contributes to the controversial results for the iron(II) complexes of 2,6-bis(pyrazol-3-yl)pyridines, preventing ‘molecular’ design of their spin-crossover activity; the synthesized complex being only the fourth of the spin-crossover (SCO)-active kind with an N,N′-disubstituted ligand.

scholarly journals Reactions of Dihaloboranes with Electron-Rich 1,4-Bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadienes

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2875
Author(s):  
Li Ma ◽  
Xiaolin Zhang ◽  
Wenbo Ming ◽  
Shengxin Su ◽  
Xiaoyong Chang ◽  
...  
Keyword(s):  
Double Bond ◽  
Nmr Spectroscopy ◽  
Diffraction Analysis ◽  
1H Nmr Spectroscopy ◽  
Variable Temperature ◽  
Organosilicon Compounds ◽  
X Ray Diffraction ◽  
X Ray ◽  
Multinuclear Nmr Spectroscopy ◽  
Bond Character

The reactions of electron-rich organosilicon compounds 1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (1), 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (2), and 1,1′-bis(trimethylsilyl)-1,1′-dihydro-4,4′-bipyridine (12) with B-amino and B-aryl dihaloboranes afforded a series of novel B=N-bond-containing compounds 3–11 and 13. The B=N rotational barriers of 7 (>71.56 kJ/mol), 10 (58.79 kJ/mol), and 13 (58.65 kJ/mol) were determined by variable-temperature 1H-NMR spectroscopy, thus reflecting different degrees of B=N double bond character in the corresponding compounds. In addition, ring external olefin isomers 11 were obtained by a reaction between 2 and DurBBr2. All obtained B=N-containing products were characterized by multinuclear NMR spectroscopy. Compounds 5, 9, 10a, 11, and 13a were also characterized by single-crystal X-ray diffraction analysis.

scholarly journals Novel reaction of 3,4-dibromofuran with azo diesters to give tetrahydropyridazinones

RSC Advances ◽  
2016 ◽  
Vol 6 (27) ◽  
pp. 22969-22972 ◽  
Author(s):  
Kati M. Aitken ◽  
R. Alan Aitken ◽  
Alexandra M. Z. Slawin
Keyword(s):  
Nmr Spectroscopy ◽  
Variable Temperature ◽  
Diels Alder ◽  
X Ray Diffraction ◽  
X Ray

Diels–Alder cycloaddition followed by rearrangement gives unexpected heterocyclic products whose structure is investigated by variable-temperature NMR spectroscopy and X-ray diffraction.

Trigold(I) Phosphine Derivatives of Clusters Containing Octahedral Rh2Ru4B-Boride Cores: The X-Ray Structure of [Rh2Ru4(CO)15Rh2Ru4B{AuPCy3}3] (Cy = cyclohexyl)

1999 ◽  
Vol 64 (6) ◽  
pp. 959-970 ◽  
Author(s):  
Andrew D. Hattersley ◽  
Catherine E. Housecroft ◽  
Arnold L. Rheingold
Keyword(s):  
Nmr Spectroscopy ◽  
Single Crystal ◽  
Boron Atom ◽  
Variable Temperature ◽  
Mass Spectrometric ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Third ◽  
Phosphine Derivatives ◽  
Derivatives Of

The reaction of [Rh(CO)2Cl]2 with [HRu4(CO)12BH]- followed by treatment with an excess (at least three-fold) of [Cy3PAuCl] (Cy = cyclohexyl) leads to the formation of [Rh2Ru4(CO)16B{AuPCy3}] (previously prepared by another route) and [Rh2Ru4(CO)15B{AuPCy3}3]. The new trigold derivative has been characterized by spectroscopic and mass spectrometric methods, and by single crystal X-ray diffraction. It possesses an octahedral Rh2Ru4 core containing an interstitial boron atom; two of the gold(I) phosphine units cap two adjacent faces and the third bridges an edge of the octahedral cage. There are no close Au···Au contacts. Reactions of [Rh2Ru4(CO)16B]- with [(R3PAu)3O]+ (R = Ph, 2-MeC6H4) resulted in the formation of [Rh2Ru4(CO)15B{AuPR3}3]; for R = Ph, two isomers in respect of the arrangements of the AuPPh3 were isolated. Fluxional processes involving the gold(I) phosphine fragments have been observed using solution variable-temperature 31P NMR spectroscopy.

B(C6F5)3-guided cyclotrimerization-rearrangement of phenylacetylene. Evidence of the (C6F5)3B−–C(H)=C+Ph intermediate in a 1,1-carboboration reaction

2016 ◽  
Vol 71 (10) ◽  
pp. 1029-1041
Author(s):  
Wanli Nie ◽  
Guofeng Sun ◽  
Chong Tian ◽  
Maxim V. Borzov
Keyword(s):  
Nmr Spectroscopy ◽  
Diffraction Analysis ◽  
Crystal Structures ◽  
Variable Temperature ◽  
Spectroscopy Study ◽  
X Ray Diffraction ◽  
X Ray ◽  
Spectral Evidence ◽  
A Minor ◽  
Zwitterionic Intermediate

AbstractIn presence of 2,2,6,6-tetramethylpiperidinium ([TMPH]+) chlorotris(pentafluorophenyl)borate ([TMPH]+[ClB(C6F5)3]−, 3), phenylacetylene undergoes an unusual cyclotrimerization-rearrangement leading to tris(pentafluorophenyl)(3,4,5-triphenylphenyl)borate anion (1) as a minor product which can be isolated and purified in a form of salts [1·(TMPH)n·Cl(n–1)] (n=3 or 5). A variable temperature and concentration NMR spectroscopy study of 3 in CDCl3 unambiguously demonstrated its ability to liberate free B(C6F5)3, which initiates cyclotrimerization and guides rearrangements towards formation of the tetraarylborate anion 1. For the previously studied “spectator” reaction between phenylacetylene and B(C6F5)3 in CDCl3, 1H, 19F, and 11B NMR-spectral evidence of the (C6F5)3B−–C(H)=C+Ph zwitterionic intermediate of the 1,1-carboboration reaction has been demonstrated. The crystal structures of [1·(TMPH)3·Cl2], the salt 3, and a 1:1 adduct of 1,3,5-tris(4-fluorophenyl)benzene and 2,4,6-tris(pentafluorophenyl)-1,3,5,2,4,6-trioxatriborinane (2) have been established by X-ray diffraction analysis.

Conformational analysis and potential anticancer activity of [Pt(phen)(L1-κS)2] studied by single crystal X-ray diffraction and variable temperature 1H and 195Pt NMR spectroscopy

2019 ◽  
Vol 43 (9) ◽  
pp. 3665-3672 ◽  
Author(s):  
Edmore F. Kangara ◽  
Tebogo Peega ◽  
Leonie Harmse ◽  
Juanita L. van Wyk ◽  
Demetrius C. Levendis ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Conformational Analysis ◽  
Single Crystal ◽  
Anticancer Activity ◽  
Variable Temperature ◽  
Stacking Interactions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Π Stacking

Conformers of [Pt(phen)(L1-κS)2] observed in solution as a result of π-stacking interactions between the unusual κS-coordinated N,N-diethyl-N′-1-naphthoylthioureato ligands and 1,10-phenanthroline.

Nature of the phase change in solid bis(isopropyl alcohol)octakis(isopropoxo)dicerium, as determined by variable-temperature x-ray diffraction and deuterium NMR spectroscopy

1991 ◽  
Vol 30 (8) ◽  
pp. 1720-1722 ◽  
Author(s):  
Beth A. Huggins ◽  
Paul D. Ellis ◽  
Peter S. Gradeff ◽  
Brian A. Vaartstra ◽  
Kenan. Yunlu ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Phase Change ◽  
Isopropyl Alcohol ◽  
Variable Temperature ◽  
Deuterium Nmr ◽  
X Ray Diffraction ◽  
X Ray

scholarly journals Iron(II) Spin Crossover Complex with the 1,2,3-Triazole-Containing Linear Pentadentate Schiff-Base Ligand and the MeCN Monodentate Ligand

Crystals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 276 ◽  
Author(s):  
Tomoe Matsuyama ◽  
Keishi Nakata ◽  
Hiroaki Hagiwara ◽  
Taro Udagawa
Keyword(s):  
Schiff Base ◽  
Schiff Base Ligand ◽  
Spin Crossover ◽  
Variable Temperature ◽  
Spin Transition ◽  
Ligand Field ◽  
X Ray Diffraction ◽  
Monodentate Ligand ◽  
X Ray ◽  
Mononuclear Iron

A mononuclear iron(II) complex bearing the linear pentadentate N5 Schiff-base ligand containing two 1,2,3-triazole moieties and the MeCN monodentate ligand, [FeIIMeCN(L3-Me-3Ph)](BPh4)2·MeCN·H2O (1), have been prepared (L3-Me-3Ph = bis(N,N′-1-Phenyl-1H-1,2,3-triazol-4-yl-methylideneaminopropyl)methylamine). Variable-temperature magnetic susceptibility measurements revealed an incomplete one-step spin crossover (SCO) from the room-temperature low-spin (LS, S = 0) state to a mixture of the LS and high-spin (HS, S = 2) species at the higher temperature of around 400 K upon first heating, which is irreversible on the consecutive cooling mode. The magnetic modulation at around 400 K was induced by the crystal-to-amorphous transformation accompanied by the loss of lattice MeCN solvent, which was evident from powder X-ray diffraction (PXRD) studies and themogravimetry. The single-crystal X-ray diffraction studies showed that the complex is in the LS state (S = 0) between 296 and 387 K. In the crystal lattice, the complex-cations and B(1)Ph4− ions are alternately connected by intermolecular CH···π interactions between the methyl group of the MeCN ligand and phenyl groups of B(1)Ph4− ions, forming a 1D chain structure. The 1D chains are further connected by P4AE (parallel fourfold aryl embrace) interactions between two neighboring complex-cations, constructing a 2D extended structure. B(2)Ph4− ions and MeCN lattice solvents exist in the spaces of the 2D layer. DFT calculations verified that the 1,2,3-triazole-containing ligand L3-Me-3Ph gives a stronger ligand field around the octahedral coordination environment of the iron(II) ion than the analogous imidazole-containing ligand H2L2Me (= bis(N,N′-2-methylimidazol-4-yl-methylideneaminopropyl)methylamine) of the known compound [FeIIMeCN(H2L2Me)](BPh4)1.5·Cl0.5·0.5MeCN (2) reported by Matsumoto et al. (Nishi, K.; Fujinami, T.; Kitabayashi, A.; Matsumoto, N. Tetrameric spin crossover iron(II) complex constructed by imidazole⋯chloride hydrogen bonds. Inorg. Chem. Commun. 2011, 14, 1073–1076), resulting in the much higher spin transition temperature of 1 than that of 2.

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