I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[12801]
Abstract: Heteroleptic [Cu(P^P)(N^N)][PF6] complexes, where N^N is a halo-substituted 2,2′-bipyridine (bpy) and P^P is either bis(2-(diphenylphosphino)phenyl)ether (POP) or 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos) have been synthesized and investigated. To stabilize the tetrahedral geometry of the copper(I) complexes, the steric demands of the bpy ligands have been increased by introducing 6- or 6,6′-halo-substituents in 6,6′-dichloro-2,2′-bipyridine (6,6′-Cl2bpy), 6-bromo-2,2′-bipyridine (6-Brbpy) and 6,6′-dibromo-2,2′-bipyridine (6,6′-Br2bpy). The solid-state structures of [Cu(POP)(6,6′-Cl2bpy)][PF6], [Cu(xantphos)(6,6′-Cl2bpy)][PF6]·CH2Cl2, [Cu(POP)(6-Brbpy)][PF6] and [Cu(xantphos)(6-Brbpy)][PF6]·0.7Et2O obtained from single crystal X-ray diffraction are described including the pressure dependence of the structure of [Cu(POP)(6-Brbpy)][PF6]. The copper(I) complexes with either POP or xantphos and 6,6′-Cl2bpy, 6-Brbpy and 6,6′-Br2bpy are orange-to-red emitters in solution and yellow-to-orange emitters in the solid state, and their electrochemical and photophysical properties have been evaluated with the help of density functional theory (DFT) calculations. The emission properties are strongly influenced by the substitution pattern that largely affects the geometry of the emitting triplet state. [Cu(POP)(6,6′-Cl2bpy)][PF6] and [Cu(xantphos)(6,6′-Cl2bpy)][PF6] show photoluminescence quantum yields of 15 and 17%, respectively, in the solid state, and these compounds were tested as luminophores in light-emitting electrochemical cells (LECs). The devices exhibit orange electroluminescence and very short turn-on times (<5 to 12 s). Maximum luminance values of 121 and 259 cd m−2 for [Cu(POP)(6,6′-Cl2bpy)][PF6] and [Cu(xantphos)(6,6′-Cl2bpy)][PF6], respectively, were achieved at an average current density of 100 A m−2. External quantum efficiencies of 1.2% were recorded for both complexes.
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May 2018
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[16314]
Abstract: Two luminescent heteroleptic Ru(II) complexes with a 2,2'‐biimidazole (biimH2) ligand form doubly hydrogen‐bonded salt bridges to 4‐sulfobenzoate anions in single crystals. The structure of one of these cation‐anion adducts shows that the biimH2 ligand is deprotonated. Its 3MLCT luminescence bands does not shift significantly under the influence of an external hydrostatic pressure, a behavior typical for these electronic transitions. In contrast, hydrostatic pressure on the other crystalline cation‐anion adduct induces a shift of proton density from the peripheral N‐H groups of biimH2 towards benzoate, leading to a pronounced red‐shift of the 3MLCT luminescence band. Such a significant and pressure‐tuneable influence from an interaction in the second coordination sphere is unprecedented in artificial small molecule‐based systems.
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Apr 2018
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[15176]
Abstract: The heteroleptic complexes [Cu(tBu-xantphos)(bpy)][PF6] and [Ag(tBu-xantphos)(bpy)][PF6], where tBu-xantphos = 9,9-dimethyl-4,5-bis(di-tert-butylphosphino)xanthene and bpy = 2,2′-bipyridine have been synthesized and their photophysical properties investigated. Single crystal X-ray diffraction studies of the compounds under ambient and increased pressure are presented; increase in pressure results in little structural perturbation. For the copper(I) complexes, the effects of changing the N^N ligand from bpy to 6-methyl-2,2′-bipyridine (6-Mebpy), 6-bromo-2,2′-bipyridine (6-Brbpy), and 4,4′-di(tert-butyl)-2,2′-bipyridine (4,4′-tBu2bpy) were also investigated. Emissions from the copper(I) complexes are weak, both in solution and the solid state and this is attributed to vibrational quenching effects of the tert-butyl substituents of the tBu-xantphos ligands.
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Feb 2018
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I19-Small Molecule Single Crystal Diffraction
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Christopher H.
Woodall
,
Gavin A.
Craig
,
Alessandro
Prescimone
,
Martin
Misek
,
Joan
Cano
,
Juan
Faus
,
Michael R.
Probert
,
Simon
Parsons
,
Stephen
Moggach
,
José
Martínez-Lillo
,
Mark
Murrie
,
Konstantin V.
Kamenev
,
Euan K.
Brechin
Diamond Proposal Number(s):
[11879]
Open Access
Abstract: Materials that demonstrate long-range magnetic order are synonymous with information storage and the electronics industry, with the phenomenon commonly associated with metals, metal alloys or metal oxides and sulfides. A lesser known family of magnetically ordered complexes are the monometallic compounds of highly anisotropic d-block transition metals; the ‘transformation’ from isolated zero-dimensional molecule to ordered, spin-canted, three-dimensional lattice being the result of through-space interactions arising from the combination of large magnetic anisotropy and spin-delocalization from metal to ligand which induces important intermolecular contacts. Here we report the effect of pressure on two such mononuclear rhenium(IV) compounds that exhibit long-range magnetic order under ambient conditions via a spin canting mechanism, with Tc controlled by the strength of the intermolecular interactions. As these are determined by intermolecular distance, ‘squeezing’ the molecules closer together generates remarkable enhancements in ordering temperatures, with a linear dependence of Tc with pressure.
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Dec 2016
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[9205]
Abstract: The effect of pressure on the intranuclear M···M separation and intermolecular
secondary interactions in the dinuclear chromium Pacman complex [Cr2(L)](C6H6) was
evaluated because this compound contains both a short Cr···Cr separation and an exogenously
bound molecule of benzene in the solid state. The electronic structure of [Cr2(L)] was
determined by electron paramagnetic resonance spectroscopy, SQUID magnetometry, and
density functional theory calculations and shows a diamagnetic ground state through
antiferromagnetic exchange, with no evidence for a Cr−Cr bond. Analysis of the solid-state
structures of [Cr2(L)](C6H6) at pressures varying from ambient to 3.0 GPa shows little
deformation in the Cr···Cr separation, i.e., no Cr−Cr bond formation, but instead a significantly increased interaction between
the exogenous arene and the chromium iminopyrrolide environment. It is therefore apparent from this analysis that [Cr2(L)]
would be best exploited as a rigid chemical synthon, with pressure regulation being used to mediate the approach and secondary
interactions of possible substrates.
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Jan 2016
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[9205]
Abstract: The diuranium(III) compound [UN′′2]2(μ-η6:η6-C6H6) (N′′=N(SiMe3)2) has been studied using variable, high-pressure single-crystal X-ray crystallography, and density functional theory . In this compound, the low-coordinate metal cations are coupled through π- and δ-symmetric arene overlap and show close metal[BOND]CH contacts with the flexible methyl CH groups of the sterically encumbered amido ligands. The metal–metal separation decreases with increasing pressure, but the most significant structural changes are to the close contacts between ligand CH bonds and the U centers. Although the interatomic distances are suggestive of agostic-type interactions between the U and ligand peripheral CH groups, QTAIM (quantum theory of atoms-in-molecules) computational analysis suggests that there is no such interaction at ambient pressure. However, QTAIM and NBO analyses indicate that the interaction becomes agostic at 3.2 GPa.
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Jun 2015
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[9205]
Abstract: The diuranium(III) compound [UN′′2]2(μ-η6:η6-C6H6) (N′′=N(SiMe3)2) has been studied using variable, high-pressure single-crystal X-ray crystallography, and density functional theory . In this compound, the low-coordinate metal cations are coupled through π- and δ-symmetric arene overlap and show close metal[BOND]CH contacts with the flexible methyl CH groups of the sterically encumbered amido ligands. The metal–metal separation decreases with increasing pressure, but the most significant structural changes are to the close contacts between ligand CH bonds and the U centers. Although the interatomic distances are suggestive of agostic-type interactions between the U and ligand peripheral CH groups, QTAIM (quantum theory of atoms-in-molecules) computational analysis suggests that there is no such interaction at ambient pressure. However, QTAIM and NBO analyses indicate that the interaction becomes agostic at 3.2 GPa.
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Jun 2015
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I19-Small Molecule Single Crystal Diffraction
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Abstract: Successive reorientations of the Jahn–Teller axes associated with the CuII ions accompany a series of pronounced structural transitions in the title compound, as is shown by X-ray crystallography and high-frequency EPR measurements. The second transition forces a dimerization involving two thirds of the CuII sites due to ejection of one of the water molecules from the coordination sphere.
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Jul 2012
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[6146]
Abstract: The application of pressure in the study of molecule-basedmaterials has gained considerable recent interest, in part dueto the high compressibilities of these materials, but alsobecause the relevant electronic/magnetic (low-energy)degrees of freedom in such materials are often very sensitiveto pressure.[1–11]For example, small changes in the coordina-tion environment around a magnetic transition-metal ion canproduce quite dramatic variations in both the on-site spin–orbit coupling as well as the exchange interactions betweensuch ions when assembled into three-dimensional (3D)networks.[2–5]However, perhaps the most compelling reasonto use pressure as a tool for understanding magneto-structuralcorrelations is the possibility of focusing investigations ona single molecule or material, as opposed to using chemicalmeans to influence the coordination environment arounda metal center, for example, by studying families of seeminglyrelated complexes that vary only in the identity of thecoordinating ligands. The latter approach obviously suffersfrom the “non-innocence” of ligands, particularly in the solidstate.The desire to study increasingly complex materials underpressure has spurred the development of sophisticatedspectroscopic tools that can be integrated with high-pressureinstrumentation.[12–15]The study of magneto-structural corre-lations requires not only precise crystallographic data, butalso detailed spectroscopic information concerning theunpaired electron(s) that give(s) rise to the magnetic proper-ties. Herein, we separately employ X-ray crystallography andhigh-frequency EPR spectroscopy to obtain high-resolutionstructural and magnetic data from oriented single-crystalsamples subjected to pressures of up to 3.5 GPa.We focus on the magnetic coordination polymer [CuF2-(H2O)2(pyz)] (1, pyz = pyrazine), which previous powderdiffraction studies have shown to undergo successive pres-sure-induced structural transitions, both of which are believedto involve dramatic reorientations of the Jahn–Teller (JT)axes associated with the CuIIions.
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Jul 2012
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Abstract: A combination of high-pressure single crystal X-ray diffraction and high-pressure SQUID magnetometry has been used to study two oxo-bridged mixed-valent Mn(III)/Mn(IV) dimers. [Mn(2)O(2)(bpy)(4)](ClO(4))(3)center dot 3CH(3)CN, (1.3CH(3)CN; bpy = 2,2'-bipyridine) has been compressed to 2.0 GPa whilst [Mn(2)O(2)(bpy)(4)](PF(6))(3)center dot 2CH(3)CN center dot 1H(2)O, (2.2CH(3)CN center dot 1H(2)O) could be measured crystallographically up to 4.55 GPa. The PF(6) salt of [Mn(2)O(2)(bpy)(4)](3+) has never been reported before while 1 has been reported as a hydrate and in a different crystallographic space group. The application of hydrostatic pressure imposes significant distortions and modifications in the structures of both complexes. In particular, in complex 1.3CH(3)CN the Mn-Mn separation is reduced by the contraction of some of the Mn-O bond lengths, whilst in 2.2CH(3)CN center dot 1H(2)O the Mn-O Mn bridging angles and the Mn-O bond lengths are substantially unchanged. Interestingly 2.2CH(3)CN center dot 1H(2)O also shows a constant contraction in nearly all the Mn-N bonds. The magnetic behaviour of the complexes has been measured up to 0.87 GPa for 1.3CH(3)CN and 0.84 GPa for 2.2CH(3)CN center dot 1H(2)O.
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Mar 2010
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