Axial ligand exchange reaction on ruthenium phthalocyanines

The electrochemistry of four novel Fe(III) complexes of the type [Fe(L)Cl], involving quadridentate ligands based on the condensation products of benzoylacetone-S-methylisothiosemicarbazone with salicylaldehyde, 5-chlorosalicylaldehyde, 3,5-dichlorosalicylaldehyde or 5-nitrosalicylaldehyde, was studied in DMF and DMSO at a GC electrode. All complexes undergo a two-step one-electron reductions, usually complicated by chemical reactions. In solutions containing Cl-, the ligand-exchange reactions Cl--DMF and Cl--DMSO take place. Stability of the chloride-containing complexes was discussed in terms of the coordinated ligand effect, oxidation state of the central atom and, in particular, of the donor effect of the solvent. Some relevant kinetic data were calculated.

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Pseudohalogenido complexes of iron-2,2′-bidipyrrins

Journal of Porphyrins and Phthalocyanines ◽

10.1142/s1088424612500538 ◽

2012 ◽

Vol 16 (05n06) ◽

pp. 641-650 ◽

Cited By ~ 14

Author(s):

Martin Bröring ◽

Silke Köhler ◽

Clemens Pietzonka

Keyword(s):

High Spin ◽

Spin State ◽

Elevated Temperatures ◽

High Spin State ◽

Spectroscopic Studies ◽

Axial Ligand ◽

Ligand Field ◽

Central Metal ◽

Exchange Reactions ◽

Dichloromethane Solution

The chlorido iron(III) complex of octaethyl-2,2′-bidipyrrin has been transformed to a series of pseudohalide complexes by ligand exchange reactions with azide, cyanate, thiocyanate and selenocyanate anions. All new complexes show the expected N-coordination of the axial ligand to the iron(III) center. In the solid state, all four species display an intermediate spin (S = 3/2) ground state, with a gradual increase of a high spin (S = 5/2) contribution at elevated temperatures for the members with the smallest ligand field strengths, i.e. the cyanato and the azido derivatives. In solution, proton NMR, and in particular IR spectroscopic studies support the interpretation of a high-spin state at ambient temperature throughout the series. The dependency of the spin state on the crystalline or dissolved state thus resembles that found for a similar series of halide derivatives before. In dichloromethane solution, the thiocyanato and selenocyanato complexes are very sensitive to aerial oxidation, forming oxacorrole and thiacorrole complexes as the only isolated products. These complexes show a S = 3/2 spin state in the solid as well as in solution, and their structural analyses prove the expected strong π-binding of the linear pseudohalide ion to the iron(III) central metal.

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Mechanism of the HF Pulse in the Thermal Atomic Layer Etch of HfO2 and ZrO2: A First Principles Study

10.26434/chemrxiv.11310860 ◽

2019 ◽

Author(s):

Rita Mullins ◽

Suresh Natarajan ◽

Simon D. Elliott ◽

Michael Nolan

Keyword(s):

First Principles ◽

Ligand Exchange ◽

Elevated Temperatures ◽

Atomic Layer ◽

Level Control ◽

Exchange Reactions ◽

Nanoscale Device ◽

High K ◽

Reaction Models ◽

High K Materials

<div>HfO2 and ZrO2 are two high-k materials that are important in the down-scaling of semiconductor devices. Atomic level control of material processing is required for fabrication of thin films of these materials at nanoscale device sizes. Thermal Atomic Layer Etch (ALE) of metal oxides, in which up to one monolayer of the material can be removed, can be achieved by sequential self-limiting fluorination and ligand-exchange reactions at elevated temperatures. However, to date a detailed atomistic understanding of the mechanism of thermal ALE of these technologically important oxides is lacking. In this paper, we investigate the hydrogen fluoride pulse in the first step in the thermal ALE process of HfO2 and ZrO2 using first principles simulations. We introduce Natarajan-Elliott analysis, a thermodynamic methodology, to compare reaction models representing the self-limiting (SL) and continuous spontaneous etch (SE) processes taking place during an ALE pulse. Applying this method to the first HF pulse on HfO2 and ZrO2 we found that thermodynamic barriers impeding continuous etch are present at ALE relevant temperatures. We performed explicit HF adsorption calculations on the oxide surfaces to understand the mechanistic details of the HF pulse. A HF molecule adsorbs dissociatively on both oxides by forming metal-F and O-H bonds. HF coverages ranging from 1.0 0.3 to 17.0 0.3 HF/nm2 are investigated and a mixture of molecularly and dissociatively adsorbed HF molecules is present at higher coverages. Theoretical etch rates of -0.61 0.02 Å /cycle for HfO2 and -0.57 0.02 Å /cycle ZrO2 were calculated using maximum coverages of 7.0 0.3 and 6.5 0.3 M-F bonds/nm2 respectively (M = Hf, Zr).</div>

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Ti(IV) phthalocyanines for dye sensitized solar cells

Journal of Porphyrins and Phthalocyanines ◽

10.1142/s1088424613500454 ◽

2013 ◽

Vol 17 (08n09) ◽

pp. 814-820 ◽

Cited By ~ 10

Author(s):

M. Salomé Rodríguez-Morgade ◽

Laia Pellejà ◽

Tomás Torres ◽

Emilio Palomares

Keyword(s):

Solar Cells ◽

Dye Sensitized Solar Cells ◽

Soret Band ◽

Axial Ligand ◽

Dye Sensitized ◽

Axial Ligands ◽

Device Efficiency ◽

Anchoring Groups ◽

Low Efficiency ◽

Sensitized Solar Cells

Ti ( IV ) phthalocyanines axially coordinated to 2,3- and 1,8-naphthalenediols have been prepared and characterized. The naphthalene axial ligands have been endowed with none, one or two sulfonate anchoring groups in order to study the performance of the dyes as DSC photosensitizers. All studied compounds showed the same efficiency. The unexpected results suggest displacement of the axial ligand with concomitant formation of a di-μ-oxotitanium-type anchoring moiety between the hydroxylated TiO 2surface and the Ti -phthalocyanine. This is probably the reason why the type of axial ligand does not play any role on the overall device efficiency. The titanium phthalocyanine absorbed in this way shows state selective electron injection were only those photons absorbed by the Soret band are capable to inject electrons into the TiO 2, while photons absorbed by the Q-band result in negligible photocurrent. This fact could explain the low efficiency of the Ti -phthalocyanines.

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Octahedral Co(III) salen complexes: the role of peripheral ligand electronics on axial ligand release upon reduction

Canadian Journal of Chemistry ◽

10.1139/cjc-2017-0277 ◽

2018 ◽

Vol 96 (2) ◽

pp. 110-118 ◽

Cited By ~ 4

Author(s):

Chen Zhang ◽

Mathew Sutherland ◽

Khrystyna Herasymchuk ◽

Ryan M. Clarke ◽

John R. Thompson ◽

...

Keyword(s):

Ligand Exchange ◽

Reduction Potential ◽

Reduction Process ◽

Axial Ligand ◽

Lewis Acidity ◽

Dominant Factor ◽

Axial Ligands ◽

Salen Complexes ◽

Reducing Conditions

A series of octahedral CoIII salen complexes (where salen represents a N2O2 bis-Schiff-base bis-phenolate framework) were prepared with axial imidazole ligating groups. When using 1-methylimidazole (1-MeIm) axial ligands, the CoIII/CoII reduction potential could be altered by 220 mV via variation of the electron-donating ability of the para-ring substituents (R = H (1), OMe (2), tBu (3), Br (4), NO2 (5), and CF3 (6)). In addition, the irreversibility of the reduction process suggested substantial geometrical changes and axial ligand exchange upon reduction to the more labile CoII oxidation state. Installing an imidazole-coumarin conjugate as the axial ligands resulted in fluorescence quenching when bound to the CoIII centre (R = H (7), OMe (8), and CF3 (9)). The redox properties and fluorescence increase upon ligand release for 7–9 were studied under reducing conditions and in the presence of excess competing ligand (1-MeIm). It was determined that the Lewis acidity of the CoIII centre was the dominant factor in controlling axial ligand exchange for this series of complexes.

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Adducts of Rhodium(II) Acetate and Rhodium(II) Pivalate with 1,8-Diazabicyclo[5.4.0]undec-7-ene

Crystals ◽

10.3390/cryst11050517 ◽

2021 ◽

Vol 11 (5) ◽

pp. 517

Author(s):

Eric D. Fussell ◽

Ampofo Darko

Keyword(s):

Close Contact ◽

Bond Distance ◽

Axial Ligand ◽

Hirshfeld Surface ◽

X Ray Diffraction ◽

X Ray ◽

Vis Spectroscopy ◽

Hirshfeld Analysis ◽

Solvent Molecules ◽

Axial Site

In this article, we describe the synthesis of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) adducts of rhodium(II) carboxylate complexes, [Rh2(μ-O2CCR3)4(DBU)2] (R = H (1), Me (2)). The DBU ligand is coordinated to the axial site in both adducts via the imido-nitrogen atom, and single-crystal X-ray diffraction analysis of 1 and 2 revealed structurally similar attributes between the compounds. The Rh–Rh bond distance is 2.4108(3) Å for 1 and 2.4143(2) Å for 2. The Rh–N distance is 2.2681(3) Å for compound 1 and 2.2587(10) Å for compound 2. Compound 1, however, crystallized with solvent molecules in its unit cell, and Hirshfeld surface analysis showed intermolecular C–H···O interactions between oxygen atoms of [Rh2(μ-O2CCH3)4] and the hydrogen of the chloroform solvent among other intermolecular close-contact interactions. The crystal structure of compound 2 was found to be devoid of solvent and showed weak intramolecular C–H···O interactions from the DBU axial ligand to the oxygens of the bridging acetates. Otherwise, Hirshfeld analysis showed that 2 was dominated by H···H interactions. UV-vis spectroscopy of both adducts was also conducted in different solvents to examine shifts attributed to the π*(Rh2) to σ*(Rh2) band.

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Axial ligand exchange reactions of ferrous phthalocyanine. Exchange of imidazole for dimethyl sulfoxide

Inorganic Chemistry ◽

10.1021/ic50080a016 ◽

1969 ◽

Vol 8 (10) ◽

pp. 2120-2123 ◽

Cited By ~ 25

Author(s):

John Gareth Jones ◽

M. V. Twigg

Keyword(s):

Dimethyl Sulfoxide ◽

Ligand Exchange ◽

Axial Ligand ◽

Exchange Reactions

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Ternary gradient metal–organic frameworks

Faraday Discussions ◽

10.1039/c7fd00045f ◽

2017 ◽

Vol 201 ◽

pp. 163-174 ◽

Cited By ~ 2

Author(s):

Chong Liu ◽

Nathaniel L. Rosi

Keyword(s):

Ligand Exchange ◽

Unit Cell ◽

X Ray Diffraction ◽

Exchange Reactions ◽

Reaction Conditions ◽

Gradient Distribution ◽

X Ray ◽

Cell Parameters ◽

Unit Cells ◽

Metal Organic

Gradient MOFs contain directional gradients of either structure or functionality. We have successfully prepared two ternary gradient MOFs based on bMOF-100 analogues, namely bMOF-100/102/106 and bMOF-110/100/102, via cascade ligand exchange reactions. The cubic unit cell parameter discrepancy within an individual ternary gradient MOF crystal is as large as ∼1 nm, demonstrating the impressive compatibility and flexibility of the component MOF materials. Because of the presence of a continuum of unit cells, the pore diameters within individual crystals also change in a gradient fashion from ∼2.5 nm to ∼3.0 nm for bMOF-100/102/106, and from ∼2.2 nm to ∼2.7 nm for bMOF-110/100/102, indicating significant porosity gradients. Like previously reported binary gradient MOFs, the composition of the ternary gradient MOFs can be easily controlled by adjusting the reaction conditions. Finally, X-ray diffraction and microspectrophotometry were used to analyse fractured gradient MOF crystals by comparing unit cell parameters and absorbance spectra at different locations, thus revealing the profile of heterogeneity (i.e. gradient distribution of properties) and further confirming the formation of ternary gradient MOFs.

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Mechanism of the HF Pulse in the Thermal Atomic Layer Etch of HfO2 and ZrO2: A First Principles Study

10.26434/chemrxiv.11310860.v1 ◽

2019 ◽

Author(s):

Rita Mullins ◽

Suresh Natarajan ◽

Simon D. Elliott ◽

Michael Nolan

Keyword(s):

First Principles ◽

Ligand Exchange ◽

Elevated Temperatures ◽

Atomic Layer ◽

Level Control ◽

Exchange Reactions ◽

Nanoscale Device ◽

High K ◽

Reaction Models ◽

High K Materials

<div>HfO2 and ZrO2 are two high-k materials that are important in the down-scaling of semiconductor devices. Atomic level control of material processing is required for fabrication of thin films of these materials at nanoscale device sizes. Thermal Atomic Layer Etch (ALE) of metal oxides, in which up to one monolayer of the material can be removed, can be achieved by sequential self-limiting fluorination and ligand-exchange reactions at elevated temperatures. However, to date a detailed atomistic understanding of the mechanism of thermal ALE of these technologically important oxides is lacking. In this paper, we investigate the hydrogen fluoride pulse in the first step in the thermal ALE process of HfO2 and ZrO2 using first principles simulations. We introduce Natarajan-Elliott analysis, a thermodynamic methodology, to compare reaction models representing the self-limiting (SL) and continuous spontaneous etch (SE) processes taking place during an ALE pulse. Applying this method to the first HF pulse on HfO2 and ZrO2 we found that thermodynamic barriers impeding continuous etch are present at ALE relevant temperatures. We performed explicit HF adsorption calculations on the oxide surfaces to understand the mechanistic details of the HF pulse. A HF molecule adsorbs dissociatively on both oxides by forming metal-F and O-H bonds. HF coverages ranging from 1.0 0.3 to 17.0 0.3 HF/nm2 are investigated and a mixture of molecularly and dissociatively adsorbed HF molecules is present at higher coverages. Theoretical etch rates of -0.61 0.02 Å /cycle for HfO2 and -0.57 0.02 Å /cycle ZrO2 were calculated using maximum coverages of 7.0 0.3 and 6.5 0.3 M-F bonds/nm2 respectively (M = Hf, Zr).</div>

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