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The luminescent properties of Au(I) and Pt(II) compounds are commonly tuned by exploiting the alkynyl ligand with varying electron density. Herein, we describe the synthesis of three new emissive transition metal compounds, tbpyPt(C2pym)2, Ph3PAuC2pym, and Cy3PAuC2pym (where HC2pym = 2-ethynylpyrimidine), verified by 1H-NMR, EA, and a single-crystal X-ray diffraction analysis. The tbpyPt(C2pym)2 complex crystallized as an Et2O solvate in the orthorhombic space group Pbca with Z = 24 with three unique Pt(II) species within the unit cell. The Cy3PAuC2pym species crystallizes in a monoclinic space group with one unique complex in the asymmetric unit. Changing the identity of the phosphine from Cy3P to Ph3P influences interactions within the unit cell. Ph3PAuC2pym, which also crystalizes in a monoclinic space group, has an aurophilic bonding interaction Au–Au distance of 3.0722(2) Å, which is not present in crystalline Cy3PAuC2pym. Regarding optical properties, the use of an electron-deficient heterocycle provides an alternate approach to blue-shifting the emission of Pt(II) transition metals' compounds, where the aryl moiety is made more electron-deficient by exploiting nitrogen within this moiety instead of the typical strategy of decorating the aryl ring with electron withdrawing substituents (e.g., fluorines). This is indicated by the blue-shift in emission that occurs in tbpyPt(C2pym)2 (λmax, emission = 512 nm) compared to the previously reported tbpyPt(C22-py)2 (where HC22-py = 2-ethynylpyridine) complex (λmax, emission = 520 nm). [ABSTRACT FROM AUTHOR]

4-(tris(4-methyl-1H-pyrazol-1-yl)methyl)aniline was prepared in a 63% yield utilizing a C–F activation strategy from a mixture of 4-(trifluoromethyl)aniline, 4-methylpyrazole, and KOH in dimethylsulfoxide (DMSO). The identity of the product was confirmed by nuclear magnetic resonance spectroscopy, infrared spectroscopy, mass spectrometry, and single-crystal analysis. An analysis of crystals grown from the layering method (CH2Cl2/acetone/pentane) indicated two distinct polymorphs of the title compound. Moreover, density functional theory calculations utilizing the MN15L density functional and the def2-TZVP basis set indicated that 4-(tris(4-methyl-1H-pyrazol-1-yl)methyl)aniline forms with similar energetics to the previously reported unmethylated analog. [ABSTRACT FROM AUTHOR]

Pyrazino-phenanthroline ligands are commonly used with transition metals as DNA intercalation agents. Herein, we report the characterization of two commonly utilized pyrazino-phenanthroline ligands, dipyrido[3,2-f:2′,3′-h]quinoxaline (dpq) and (benzo[i]dipyrido[3,2-a:2′,3′c]phenazine (dppn), by single-crystal X-ray diffraction. Additionally, the characterization of [Ir(ppy)2(dppn)][PF6], where Hppy = 2-phenylpyridine, by single-crystal X-ray diffraction is described. Both the dpq and dppn ligands crystallize as chloroform solvates where the chloroform molecule occupies the equivalent binding pocket of a metal in metal complexes of these ligands. These pyrazino-phenanthrolines are largely planar, with the dppn ligand displaying a slight twist. When the dppn ligand is coordinated to iridium(III), the dppn ligand on the resulting complex displays a significant degree of bending along the longitudinal direction of the ligand. This iridium (III) complex crystallizes as a CH2Cl2 and Et2O solvate and due to the volatility of these solvents these crystals are only stable for a few seconds outside of the mother liquor. The structures of the free ligands and the [Ir(ppy)2(dppn)][PF6] complex all display extensive π stacking interactions. [ABSTRACT FROM AUTHOR]

Bis[µ5-(tert-butoxycarbonyl)cyclopentadienyl]dichloridotitanium(IV), [Ti(C10- H13O2)2Cl2], was synthesized from LiCpCOOt-Bu using TiCl4, and was characterized by single-crystal X-ray diffraction and 1H NMR spectroscopy. The distorted tetrahedral geometry about the central titanium atom is relatively unchanged compared to Cp2TiCl2. The complex exhibits elongation of the titanium-- cyclopentadienyl centroid distances [2.074 (3) and 2.070 (3) Å] and a contraction of the titanium--chlorine bond lengths [2.3222 (10) Å and 2.3423 (10) Å ] relative to Cp2TiCl2. The dihedral angle formed by the planes of the Cp rings [52.56 (13)] is smaller than seen in Cp2TiCl2. Both ester groups extend from the same side of the Cp rings, and occur on the same side of the complex as the chlorido ligands. The complex may serve as a convenient synthon for titanocene complexes with carboxylate anchoring groups for binding to metal oxide substrates. [ABSTRACT FROM AUTHOR]

Iron(II)-to-titanium(IV) metal-to-metal-charge transfer (MMCT) is important in the photosensitization of TiO2 by ferrocyanide, charge transfer in solid-state metal-oxide photocatalysts, and has been invoked to explain the blue color of sapphire, blue kyanite, and some lunar material. Herein, a series of complexes with alkynyl linkages between ferrocene (Fc) and TiIV has been prepared and characterized by UV-vis spectroscopy and electrochemistry. Complexes with two ferrocene substituents include Cp2Ti(C2Fc)2, Cp*2Ti(C2Fc)2, and Cp2Ti(C4Fc)2. Complexes with a single ferrocene utilize a titanocene with a trimethylsilyl derivatized Cp ring, TMSCp, and comprise the complexes TMSCp2Ti(C2Fc)(C2R), where R = C6H5, p-C6H4CF3, and CF3. The complexes are compared to Cp2Ti(C2Ph)2, which lacks the second metal. Cyclic voltammetry for all complexes reveals a reversible TiIV/III reduction wave and an FeII/III oxidation that is irreversible for all complexes except TMSCp2Ti(C2Fc)(C2CF3). All of the complexes with both Fc and Ti show an intense absorption (4000 M-1cm-1 < ε < 8000 M-1cm-1) between 540 and 630 nm that is absent in complexes lacking a ferrocene donor. The energy of the absorption tracks with the difference between the TiIV/III and FeIII/II reduction potentials, shifting to lower energy as the difference in potentials decreases. Reorganization energies, λ, have been determined using band shape analysis (2600 cm-1 < λ < 5300 cm-1) and are in the range observed for other donor-acceptor complexes that have a ferrocene donor. Marcus-Hush-type analysis of the electrochemical and spectroscopic data are consistent with the assignment of the low-energy absorption as a MMCT band. TD-DFT analysis also supports this assignment. Solvatochromism is apparent for the MMCT band of all complexes, there being a bathochromic shift upon increasing polarizability of the solvent. The magnitude of the shift is dependent on both the electron density at TiIV and the identity of the linker between the titanocene and the Fc. Complexes with a MMCT are photochemically stable, whereas Cp2Ti(C2Ph)2 rapidly decomposes upon photolysis. [ABSTRACT FROM AUTHOR]

2-(Dimethylamino)pyridine(2-DMAP) and 2-(dimethylamino)pyrimidinederivatives form η2-bound complexes with the dearomatizationagent {TpW(NO)(PMe3)} that are each capable of undergoinga double protonation. In the case of 2-DMAP, the resulting π-allylspecies reacts with the α-carbon of thiophene or 2-methylfuran,thereby coupling the heterocyclic rings. In the case of the thiophene-derivedproduct, subsequent oxidative decomplexation using ceric ammoniumnitrate affords a novel organic amidine derivative. Examples of tungsten-promotedacetylation and fluorination of the aminopyridine ring are also described. [ABSTRACT FROM AUTHOR]

Thecomplexes TpW(NO)(PMe3)(L), where L = 2H-phenol, 2H-p-cresol, 2H-5,6,7,8-tetrahydro-2-naphthol, 2H-N,N-dimethylanilinium were cyclopropanatedusing Simmons–Smith conditions. Cyclopropanated derivativesof 2H-N,N-dimethylanilinium wereselectively ring-opened with HOTf/MeCN to form allylic species, whichcould be coupled with various nucleophiles. The nucleophilic additionoccurs antito the metal fragment, as determinedby X-ray crystallography. Moreover, the cyclopropane ring openingoccurs regioselectively, owing to the stabilization of the allyliccation by the metal fragment. The resulting ligands can, in some cases,be removed from the metal by oxidative decomplexation using cericammonium nitrate (CAN). [ABSTRACT FROM AUTHOR]

The complexes TpW(NO)(PMe3)(L), where L =phenol, N,N-dimethylanilinium, or naphthalene, undergoprotonation followed by addition of an aromatic nucleophile. The additionof aromatic molecules occurs at the para carbon of the phenol or anilinering or the beta carbon of the naphthalene. The addition occurs antito the metal fragment, as determined by X-ray crystallography. Inthe case where L = phenol or N,N-dimethylanilinium,treatment of the bound arene with an electrophilic heteroatom followedby an aromatic nucleophile sets two stereocenters, with both additionsoccurring anti to the metal. The resultant ligands have been removedfrom the metal by oxidative decomplexation using ceric ammonium nitrate. [ABSTRACT FROM AUTHOR]

Bis[µ5-(tert-butoxycarbonyl)cyclopentadienyl]dichloridotitanium(IV), [Ti(C10- H13O2)2Cl2], was synthesized from LiCpCOOt-Bu using TiCl4, and was characterized by single-crystal X-ray diffraction and 1H NMR spectroscopy. The distorted tetrahedral geometry about the central titanium atom is relatively unchanged compared to Cp2TiCl2. The complex exhibits elongation of the titanium-- cyclopentadienyl centroid distances [2.074 (3) and 2.070 (3) Å] and a contraction of the titanium--chlorine bond lengths [2.3222 (10) Å and 2.3423 (10) Å ] relative to Cp2TiCl2. The dihedral angle formed by the planes of the Cp rings [52.56 (13)] is smaller than seen in Cp2TiCl2. Both ester groups extend from the same side of the Cp rings, and occur on the same side of the complex as the chlorido ligands. The complex may serve as a convenient synthon for titanocene complexes with carboxylate anchoring groups for binding to metal oxide substrates. [ABSTRACT FROM AUTHOR]

The title cyclo-metalated distorted octa-hedral iridium complex, [Ir(C 11 H 6 F 2 N) 2 (C 12 H 12 N 2 O 2 )]PF 6 , exhibits elongated Ir-N bonds to the dimeth-oxy bi-pyridine ligand [2.128 (3) and 2.136 (3) Å] where these nitro-gen atoms are trans to the Ir-C bonds of the two cyclo-metalating di-fluoro-phenyl-pyridine ligands. The angles between the mean planes of the phenyl and pyridyl fragments within the individual ligands range from 3.5 (2) to 11.4 (2)° to deviate slightly from coplanarity., (© Shevlin et al. 2022.)

Transition-metal complexes that undergo ligand-to-metal charge transfer (LMCT) to d 0 metals are of interest as possible photocatalysts due to the lack of deactivating d-d states. Herein, the synthesis and characterization of nine titanocene complexes of the formula Cp 2 Ti(C 2 ·MX (where Ar = phenyl, dimethylaniline, or triphenylamine; and MX = CuCl, CuBr, or AgCl) are presented. Solid-state structural characterization demonstrates that MX coordinates to the alkyne tweezers and CuX coordination has a greater structural impact than AgCl. All complexes, including the parent complexes without coordinated MX, are brightly emissive at 77 K (emission max between 575 and 767 nm), with the coordination of MX redshifting the emission in all cases except for the coordination of AgCl into Cp 2 ·MX (where Ar = phenyl, dimethylaniline, or triphenylamine; and MX = CuCl, CuBr, or AgCl) are presented. Solid-state structural characterization demonstrates that MX coordinates to the alkyne tweezers and CuX coordination has a greater structural impact than AgCl. All complexes, including the parent complexes without coordinated MX, are brightly emissive at 77 K (emission max between 575 and 767 nm), with the coordination of MX redshifting the emission in all cases except for the coordination of AgCl into Cp 2 Ti(C 2 Ph) 2 . TDDFT investigations suggest that emission is dominated by arylalkynyl-to-titanium 3 LMCT in all cases except Cp 2 Ti(C 2 Ph) 2 ·CuBr, which is dominated by CuBr-to-Ti charge transfer. In room-temperature fluid solution, only Cp 2 Ti(C 2 Ph) 2 and Cp 2 Ti(C 2 Ph) 2 ·AgCl are emissive, albeit with photoluminescent quantum yields ≤2 × 10 -4 . The parent complexes photodecompose in room-temperature solution with quantum yields, Φ rxn by two to three orders of magnitude. There is a clear trend that Φ rxn increases as the emission energy increases. This trend is consistent with a competition between energy-gap-law controlled nonradiative decay and thermally activated intersystem crossing between the rxn increases as the emission energy increases. This trend is consistent with a competition between energy-gap-law controlled nonradiative decay and thermally activated intersystem crossing between the 3 LMCT state and the singlet transition state for decomposition.