Alkali metal cation complexation and solvent interactions by robust chromium(III) fluoride complexes

Birk, Torben; Magnussen, Magnus; Piligkos, Stergios; Weihe, Høgni; Holten, Anders; Bendix, Jesper

doi:10.1016/j.jfluchem.2010.06.003

Cited by 26 publications

(29 citation statements)

References 35 publications

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“…with the ligands in n-BuOH or dmf, respectively, following litera-ture methods. 20 The IR spectra of the solids confirm the presence of water and show two ν(Cr-F) bands for [CrF 3 (Me 3 -tacn)]•3.5H 2 O, as expected for a fac octahedral configuration in C 3v symmetry, whereas one very broad band is seen for [CrF 3 (terpy)]•4H 2 O (three bands are expected in a mer C 2v symmetry, but not resolved). The diffuse reflectance spectra of the complexes are shown in Fig.…”

Section: Resultsmentioning

confidence: 63%

“…The trifluoro complexes have a strong tendency to form H-bonding interactions between the fluorides and water molecules in the lattice; 8 this has often led to discrepancy in the number of water molecules co-crystallised in the lattice compared to the literature 19,20,24 and in some cases in this work leading to differences in the number of associated water molecules between the bulk materials and the crystal structures (for example [MF 3 (Me 3 -tacn)], M = Mn, Co, have two water molecules in the bulk, but four in the crystal structure). This might be due to differences in the crystallisation methods employed and the length of time the bulk materials were dried in vacuo.…”

Section: Resultsmentioning

confidence: 99%

“…16 In particular, complexes of ammonia and amines have been studied extensively for their absorption and emission properties, contributing to the development of inorganic electronic spectroscopy. 17 The neutral species [CrF 3 (bipy)(OH 2 )], 18 fac-[CrF 3 (Me 3 -tacn)] 19,20 and mer-[CrF 3 (terpy)] 20 have also been reported and structurally characterised. Complexes with tetradentate N-donor ligands can also be found in the literature.…”

Section: Introductionmentioning

confidence: 99%

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Exploring transition metal fluoride chelates – synthesis, properties and prospects towards potential PET probes

et al. 2019

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Section: Resultsmentioning

confidence: 63%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Exploring transition metal fluoride chelates – synthesis, properties and prospects towards potential PET probes

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“…However, DFT modeling of the interaction between neutral trifluorido complexes of Cr(III) and Na + in vacuum as well as in solution revealed a pronounced breakdown of the commonly assumed additivity of ligand-field contributions. 9 Thus the actual decrease of the donor strength of fluoride upon ligation or solvation is more than compensated by an increased donation from the auxiliary amine, or as demonstrated here, imine ligands. The change in absorption spectrum results in isosbestic points suggesting only two spectroscopically distinct coordination environments of the chromium(III) as the Gd/Cr-ratio is increased.…”

Section: ■ Results and Discussionmentioning

confidence: 72%

“…However, shifts of the same sign and even larger magnitude were found for fac-[CrF 3 (Me 3 tacn)] interacting with Na + ions in 2-propanol. 9 It has also generally been found that Cr(III) fluoride complexes exhibit solvatochromism with hypsochromic shifts upon moving to more strongly proton donating solvents. 16 It has been suggested that this effect stems from a different radial dependence of the LF σ-and π-parameters for fluoride.…”

Section: ■ Results and Discussionmentioning

confidence: 98%

Fluoride Bridges as Structure-Directing Motifs in 3d-4f Cluster Chemistry

et al. 2012

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The use of kinetically robust chromium(III) fluorido complexes as synthons for mixed 3d-4f clusters is reported. The tendency toward linear {Cr(III)-F-Ln(III)} units dictates the cluster topology. Specifically, we show that reaction of cis-[Cr(III)F(2)(NN)(2)]NO(3) (NN = 1,10-phenanthroline ("phen") or 2,2'-bipyridine ("bpy")) with Ln(NO(3))(3)·xH(2)O produces isostructural series of molecular {Ln(2)Cr(2)} squares (1-9) with linear fluoride bridges. In a parallel fashion, fac-[Cr(III)F(3)L], where L = N,N',N″-trimethyl-1,4,7-triazacyclononane ("Me(3)tacn"), reacts with Nd(NO(3))(3)·6H(2)O to form a fluoride-centered penta-nuclear complex and fac-[Cr(III)F(3)L'], with L' = 1,1,1-tris-((methylamino)methylethane) ("Me(3)tame"), reacts with [Ln(hfac)(3)(H(2)O)(2)] (hfacH = 1,1,1,5,5,5-hexafluoroacetylacetone) to yield an isostructural series of {Ln(3)Cr(2)} (10-14) trigonal bipyramids with no central ligand. The formation of the latter is accompanied by a partial solvolysis of the Cr(III) precursor but without formation of insoluble LnF(3). The magnetic properties of the gadolinium containing clusters allow quantification of fluoride-mediated, antiferromagnetic Gd-Cr exchange interactions of magnitude between 0.14 cm(-1) and 0.71 cm(-1) (Ĥ = J(12)Ŝ(1)·Ŝ(2) formalism) and vanishingly small J(Gd-Gd) of 0.06(0) cm(-1). The large spin and small anisotropy together with weak exchange interactions in the {Gd(3)Cr(2)} (11) cluster give rise to a very large magneto-caloric effect of -ΔS(m) = 28.7 J kg(-1) K(-1) (μ(0)H = 90 to 0 kOe).

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Fluoride as Ligand: Chemistry of Some New Terminal and Bridged Systems

Birk

2013

ChemistryOpen

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A comprehensive and unifying theme in this thesis has been the synthesis and characterization of new coordination polymers and metal-organic networks. The common structural organizing element for these systems is the fluoride ion, which, according to the Pearson classification, is a "hard" or "class a" ligand. Accordingly, it is expected that fluoride would be best suited as a bridging ligand in systems with correspondingly "hard" metal ions. The regions of the periodic table of primary relevance would thus be the early transition metals, but also main-group elements from group I and II (as well as Al The studied systems are all based on the 3dÀF unit where either Cr III or Mn III coordinates a minimum of one fluorido ligand. The 3dÀF unit has been studied in proper mononuclear systems but also in polynuclear or polymeric systems connected through unsupported bridging by fluorido ligand(s). This bridging is of both homo-and, for chromium also, heterometallic character. For the latter type of systems, completely novel classes of compounds containing either alkali metals (3dÀFÀns) or lanthanides (3dÀFÀ4f) were synthesized and characterized structurally and magnetically.A + and cis-[Cr(phen) 2 (H 2 O)(F)] 2 + (py = pyridine, phen = 1,10-phenantroline, bpy = 2,2'-bipyridine) as precursors. These metal-containing building blocks (or ligands) can be viewed as synthons for the fluoride-containing part of the final complex. The fluorido ligands in these robust synthons are fixed with respect to configuration, and due to the robustness of the synthons undesirable ligand substitution is avoided. This is particularly important as it prevents or retards metathesis reactions catalyzed by reaction partners, including precipitation reactions involving relatively insoluble simple fluorides. The stereochemical control of the disposition of the fluorido ligands in the starting materials provides the opportunity for controlling the structures of the resulting polynuclear or polymeric products. This fairly rare situation of stereochemical control is contingent on the preferential linear bridging by fluoride, which is a recurrent motif in the systems studied here and in agreement with established chemistry of fluoride as a bridging ligand. The applicability and generality of the method is exemplified by reaction with hard metal ions from different parts of the periodic table. A graphical overview of the investigated systems based on the synthetic route to systems with unsupported, bridging fluorido ligands is given in Scheme 1.The following sections discuss the overall results of the synthetic route to systems with unsupported, bridging fluorido ligands (3dÀFÀns, 3dÀFÀ3d and 3dÀFÀ4f).

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Alkali metal cation complexation and solvent interactions by robust chromium(III) fluoride complexes

Cited by 26 publications

References 35 publications

Exploring transition metal fluoride chelates – synthesis, properties and prospects towards potential PET probes

Exploring transition metal fluoride chelates – synthesis, properties and prospects towards potential PET probes

Fluoride Bridges as Structure-Directing Motifs in 3d-4f Cluster Chemistry

Fluoride as Ligand: Chemistry of Some New Terminal and Bridged Systems

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