| 1. |
- Hossain, Md Kamal, et al.
(författare)
-
Dioxomolybdenum(VI) complexes of hydrazone phenolate ligands - syntheses and activities in catalytic oxidation reactions
- 2021
-
Ingår i: Journal of the Indian Chemical Society. - : Elsevier BV. - 0019-4522. ; 98:2
-
Tidskriftsartikel (refereegranskat)abstract
- The new cis-dioxomolybdenum (VI) complexes [MoO2(L2)(H2O)] (2) and [MoO2(L3)(H2O)] (3) containing the tridentate hydrazone-based ligands (H2L2 = N'-(3,5-di-tert-butyl-2-hydroxybenzylidene)-4-methylbenzohydrazide and H2L3 = N'-(2-hydroxybenzylidene)-2-(hydroxyimino)propanehydrazide) have been synthesized and characterized via IR, 1H and 13C NMR spectroscopy, mass spectrometry, and single crystal X-ray diffraction analysis. The catalytic activities of complexes 2 and 3, and the analogous known complex [MoO2(L1)(H2O)] (1) (H2L1 = N'-(2-hydroxybenzylidene)-4-methylbenzohydrazide) have been evaluated for various oxidation reactions, viz. oxygen atom transfer from dimethyl sulfoxide to triphenylphosphine, sulfoxidation of methyl-p-tolylsulfide or epoxidation of different alkenes using tert-butyl hydroperoxide as terminal oxidant. The catalytic activities were found to be comparable for all three complexes, but complexes 1 and 3 showed better catalytic performances than complex 2, which contains a more sterically demanding ligand than the other two complexes.
|
|
| 2. |
- Kuzevanova, Iryna, et al.
(författare)
-
Spin crossover in iron(ii) Hofmann clathrates analogues with 1,2,3-triazole
- 2021
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 50, s. 9250-9258
-
Tidskriftsartikel (refereegranskat)abstract
- Hofmann-like cyanometallic complexes represent one of the biggest and well-known classes of FeII spin-crossover compounds. In this paper, we report on the first FeII Hofmann clathrate analogues with unsubstituted 1,2,3-triazole, which exhibit temperature induced spin transition. Two new coordination polymers with the general formula [FeII(1,2,3-triazole)2MII(CN)4] (M = Pt, Pd) undergo abrupt hysteretic spin crossover in the range of 190–225 K as revealed by magnetic susceptibility measurements. Two compounds are isostructural and are built of infinite cyanometallic layers which are supported by 1,2,3-triazole ligands. The thermal hysteresis loop is very stable at different scan rates from 0.5 to 10 K min−1. The compounds display strong thermochromic effect, changing their colour from pink in the low-spin state to white in the high-spin state. Our findings show that 1,2,3-triazole is suitable for elaboration of spin-crossover Hofmann clathrate analogues, and its use instead of more classical azines can advantageously expand this family of complexes.
|
|
| 3. |
- Malinkin, Sergey O., et al.
(författare)
-
Novel pyrazolate-based copper(II) [2 x 2] grid complexes: Synthesis, structure and properties
- 2012
-
Ingår i: Inorganica Chimica Acta. - : Elsevier BV. - 0020-1693. ; 392, s. 322-330
-
Tidskriftsartikel (refereegranskat)abstract
- 5-Acetyl-substituted pyrazole-3-carboxylic acid (H2L) forms [2 x 2] grid-like tetranuclear Cu(II) complexes with four five-coordinated copper(II) ions bridged by pyrazolate groups. Despite a significant dissociation of [Cu4L4(H2O)(4)]center dot 4H(2)O (1) in aqueous solution(1), it was possible to substitute the coordinated water molecules by pyridine ligands or azide anions. The resulting tetranuclear complexes [Cu4L4Py4]center dot 2H(2)O (2) and Na-4[Cu4L4(N-3)(4)]center dot 7MeOH (3) were isolated and studied by X-ray diffraction analysis. In 2 and 3 the azide anions or pyridine molecules complete the distorted square-pyramidal coordination of each copper(II) center. Magnetic susceptibilities of the obtained compounds have been measured by SQUID techniques. Simulation of the data using a Heisenberg spin Hamiltonian approach showed that the bridges between the metals mediate weak intramolecular antiferromagnetic coupling (J in the range -13.3 to -17.1 cm (1)) and lead to a singlet ground state in all cases. (C) 2012 Elsevier B.V. All rights reserved.
|
|
| 4. |
- Malinkin, Sergey O., et al.
(författare)
-
Zinc(II) Complexes with Asymmetric 3,5-Substituted 1H-Pyrazoles
- 2012
-
Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1099-0682 .- 1434-1948. ; :10, s. 1639-1649
-
Tidskriftsartikel (refereegranskat)abstract
- Two new pyrazolate-based ligands, N'-[1-(3-acetyl-4-methyl-1H-pyrazol-5-yl)ethylidene]-2-(hydroxyimino)propanehydrazide (L1) and 5-[(E)-1-(2-{(E)-2-(hydroxyimino}propanoyl}hydrazono)ethyl]-4-methyl-1H-pyrazole-3-carboxylic acid (L2), were synthesized and studied for zinc(II) complexation. A set of pH-dependent UV/Vis measurements has been performed to determine the complex formation properties of L2. According to the calculations, in solution, L2 forms variously protonated mononuclear (ZnII/L2 = 1:1) and dinuclear (ZnII/L2 = 2:1) complexes. The reaction of the deprotonated ligands with hydrated ZnII salts and slow diffusion of ammonia into the reaction mixtures gave mononuclear [Zn(L1-2H)(NH3)2]center dot DMF (1) and trinuclear mu-pyrazolato-bridged [Zn3(L2-3H)2(NH3)5]center dot 4H2O (3). In both complexes, the zinc ions are in the same distorted trigonal-bipyramidal environment, coordinated to two nitrogen atoms of the ammonia and one oxygen and two nitrogen atoms of the pyrazolate and hydrazide groups. The molecular structures of all of the ligands and complexes have been elucidated by X-ray crystallography.
|
|
| 5. |
- Plutenko, Maksym O., et al.
(författare)
-
Crystal structure of a water oxidation catalyst solvate with composition (NH4)2[FeIV(L-6H)]·3CH3COOH (L = clathrochelate ligand)
- 2024
-
Ingår i: Acta Crystallographica Section E Crystallographic Communications. - : International Union Of Crystallography. - 2056-9890. ; 80:1, s. 25-28
-
Tidskriftsartikel (refereegranskat)abstract
- The synthetic availability of molecular water oxidation catalysts containing high-valent ions of 3d metals in the active site is a prerequisite to enabling photo- and electrochemical water splitting on a large scale. Herein, the synthesis and crystal structure of diammonium {μ-1,3,4,7,8,10,12,13,16,17,19,22-dodecaazatetracyclo[8.8.4.13,17.18,12]tetracosane-5,6,14,15,20,21-hexaonato}ferrate(IV) acetic acid trisolvate, (NH4)2[FeIV(C12H12N12O6)]·3CH3COOH or (NH4)2[FeIV(L–6H)]·3CH3COOH is reported. The FeIV ion is encapsulated by the macropolycyclic ligand, which can be described as a dodeca-aza-quadricyclic cage with two capping triazacyclohexane fragments making three five- and six six-membered alternating chelate rings with the central FeIV ion. The local coordination environment of FeIV is formed by six deprotonated hydrazide nitrogen atoms, which stabilize the unusual oxidation state. The FeIV ion lies on a twofold rotation axis (multiplicity 4, Wyckoff letter e) of the space group C2/c. Its coordination geometry is intermediate between a trigonal prism (distortion angle φ = 0°) and an antiprism (φ = 60°) with φ = 31.1°. The Fe—N bond lengths lie in the range 1.9376 (13)–1.9617 (13) Å, as expected for tetravalent iron. Structure analysis revealed that three acetic acid molecules additionally co-crystallize per one iron(IV) complex, and one of them is positionally disordered over four positions. In the crystal structure, the ammonium cations, complex dianions and acetic acid molecules are interconnected by an intricate system of hydrogen bonds, mainly via the oxamide oxygen atoms acting as acceptors.
|
|
| 6. |
- Shylin, Sergii I., et al.
(författare)
-
Expanding manganese(iv) aqueous chemistry : unusually stable water-soluble hexahydrazide clathrochelate complexes
- 2021
-
Ingår i: Chemical Communications. - Cambridge : Royal Society of Chemistry. - 1359-7345 .- 1364-548X. ; 57:84, s. 11060-11063
-
Tidskriftsartikel (refereegranskat)abstract
- Mn cage complexes are rare, and the ones successfully isolated in the solid state are not stable in water and organic solvents. Herein, we present the first report of mononuclear Mn clathrochelates, in which the encapsulated metal exists in the oxidation state +4. The complexes are extremely stable in the crystalline state and in solutions and show rich redox chemistry.
|
|
| 7. |
- Bibik, Yurii S., et al.
(författare)
-
Cooperative Spin Crossover above Room Temperature in the Iron(II) Cyanoborohydride–Pyrazine Complex
- 2022
-
Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 61:37, s. 14761-14769
-
Tidskriftsartikel (refereegranskat)abstract
- Hysteretic spin crossover in coordination complexes of 3d-metal ions represents one of the most spectacular phenomena of molecular bistability. In this paper we describe a self-assembly of pyrazine (pz) and Fe(BH3CN)2 that afforded the new 2D coordination polymer [Fe(pz)2(BH3CN)2]∞. It undergoes an abrupt, hysteretic spin crossover (SCO) with a T1/2 of 338 K (heating) and 326 K (cooling) according to magnetic susceptibility measurements. Mössbauer spectroscopy revealed a complete transition between the low-spin (LS) and the high-spin (HS) states of the iron centers. This LS-to-HS transition induced an increase of the unit cell volume by 10.6%. Meanwhile, a modulation of multiple [C–Hδ+···Hδ−–B] dihydrogen bonds stimulates a contraction in direction c (2.2%). The simplicity of the synthesis, mild temperatures of transition, a pronounced thermochromism, stability upon thermal cycling, a striking volume expansion upon SCO, and an easy processability to composite films make this new complex an attractive material for switchable components of diverse applications.
|
|
| 8. |
- Shylin, Sergii I., et al.
(författare)
-
Efficient visible light-driven water oxidation catalysed by an iron(IV) clathrochelate complex
- 2019
-
Ingår i: Chemical Communications. - 1359-7345 .- 1364-548X. ; 55:23, s. 3335-3338
-
Tidskriftsartikel (refereegranskat)abstract
- A water-stable FeIV clathrochelate complex catalyzes fast and homogeneous photochemical oxidation of water to dioxygen with a turnover frequency of 2.27 s−1 and a maximum turnover number of 365. An FeV intermediate generated under catalytic conditions is trapped and characterised using EPR and Mössbauer spectroscopy.
|
|
| 9. |
- Shylin, Sergii I., et al.
(författare)
-
Photoinduced hole transfer from tris(bipyridine)ruthenium dye to a high-valent iron-based water oxidation catalyst
- 2019
-
Ingår i: Faraday discussions. - : ROYAL SOC CHEMISTRY. - 1359-6640 .- 1364-5498. ; 215, s. 162-174
-
Tidskriftsartikel (refereegranskat)abstract
- An efficient water oxidation system is a prerequisite for developing solar energy conversion devices. Using advanced time-resolved spectroscopy, we study the initial catalytic relevant electron transfer events in the light-driven water oxidation system utilizing [Ru(bpy)(3)](2+) (bpy = 2,2 '-bipyridine) as a light harvester, persulfate as a sacrificial electron acceptor, and a high-valent iron clathrochelate complex as a catalyst. Upon irradiation by visible light, the excited state of the ruthenium dye is quenched by persulfate to afford a [Ru(bpy)(3)](3+)/SO4- pair, showing a cage escape yield up to 75%. This is followed by the subsequent fast hole transfer from [Ru(bpy)(3)](3+) to the Fe-IV catalyst to give the long-lived Fe-V intermediate in aqueous solution. In the presence of excess photosensitizer, this process exhibits pseudo-first order kinetics with respect to the catalyst with a rate constant of 3.2(1) x 10(10) s(-1). Consequently, efficient hole scavenging activity of the high-valent iron complex is proposed to explain its high catalytic performance for water oxidation.
|
|
| 10. |
- Sirenko, Valerii Y., et al.
(författare)
-
Nature of cyanoargentate bridges defining spin crossover in new 2D Hofmann clathrate analogues
- 2024
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 53:9, s. 4251-4259
-
Tidskriftsartikel (refereegranskat)abstract
- Chemical composition is leading among the numerous factors that determine the spin transition properties of coordination compounds. Classic dicyanometallic bridges {M(CN)2}− are commonly used to build Hofmann-like spin-crossover frameworks, but some extended bridges are also synthetically available. In this paper, we describe a successful synthesis of two very similar spin-crossover frameworks that differ in the cyanometallic bridges involved, namely [Fe(etpz)2{Ag(CN)2}2] (1) and {Fe(etpz)2[Ag2(CN)3][Ag(CN)2]} (2) (where etpz = 2-ethylpyrazine). Magnetic and Mössbauer studies demonstrated the occurrence of abrupt one-step high-spin (HS) ↔ low-spin (LS) transitions for both complexes. The spin transition temperatures are T1/2 ↓ = 233 K and T1/2 ↑ = 243 K for 1 and T1/2 ↓ = 188 K and T1/2 ↑ = 191 K for 2 with thermal hysteresis loops of 10 K for 1 and 3 K for 2. The bridging mononuclear [Ag(CN)2]− units and FeII cations assemble to form infinite 2D layers in the structure of 1. Interestingly, compound 2 forms 2D layers of FeII cations bridged by both binuclear [Ag2(CN)3]− and mononuclear [Ag(CN)2]− units. The structures of 1 and 2 comprise different types of intermolecular interactions including Ag⋯Ag and Ag⋯Netpz, which induce the creation of supramolecular 3D frameworks. The synergy between metallophilic interactions and the spin transition is also confirmed by the variation of Ag⋯Ag distances during spin crossover. The characterization of such analogues allowed us to analyze in detail the effect of the cyanometallic bridge on the structure of new frameworks and on the bistability in Hofmann-like complexes.
|
|
