3 research outputs found
Experimental and Theoretical Investigation for the Level of Conjugation in Carbazole-Based Precursors and Their Mono‑, Di‑, and Polynuclear Pt(II) Complexes
A series of trimethylsilyl-protected
monoalkynes (Me<sub>3</sub>SiCC–R) and bis-alkynes
(Me<sub>3</sub> SiCC–R–CCSiMe<sub>3</sub>) incorporating carbazole spacer groups (R = carbazole-2-yl, carbazole-3-yl,
carbazole-2,7-diyl, <i>N</i>-(2-ethylhexyl)Âcarbazole-2,7-diyl,
carbazole-3,6-diyl, <i>N</i>-(2-ethylhexyl)Âcarbazole-3,6-diyl),
together with the corresponding terminal monoalkynes (H–CC–R)
and bis-alkynes (H–CC–R–CC–H),
have been synthesized and characterized. The CuI-catalyzed dehydrohalogenation
reaction between <i>trans</i>-[(Ph)Â(Et<sub>3</sub>P)<sub>2</sub>PtCl], <i>trans</i>-[(Et<sub>3</sub>P)<sub>2</sub>PtCl<sub>2</sub>], and <i>trans</i>-[(P<sup><i>n</i></sup>Bu<sub>3</sub>)<sub>2</sub>PtCl<sub>2</sub>] and the terminal
alkynes in <sup><i>i</i></sup>Pr<sub>2</sub>NH/CH<sub>2</sub>Cl<sub>2</sub> affords a series of PtÂ(II) mono- and diynes, while
the dehydrohalogenation polycondensation reactions with <i>trans</i>-[(P<sup><i>n</i></sup>Bu<sub>3</sub>)<sub>2</sub>PtCl<sub>2</sub>] under similar reaction conditions yields four PtÂ(II) poly-ynes
of the form <i>trans</i>-[(P<sup><i>n</i></sup>Bu<sub>3</sub>)<sub>2</sub>Pt–CC–R–CC−]<sub><i>n</i></sub>. The acetylide-functionalized carbazole
ligands and the mono-, di-, and polynuclear PtÂ(II) σ-acetylide
complexes have been characterized spectroscopically, with a subset
analyzed using single-crystal X-ray diffraction. The PtÂ(II) mono-,
di-, and poly-ynes incorporating the carbazole spacers are soluble
in common organic solvents, and solution absorption spectra show a
consistent red-shift between the 2- and 2,7- as well as 3- and 3,6-carbazole
complexes. Computational modeling is used to explain the observed
spectral shifts, which are related to the enhanced electronic delocalization
in the latter systems. These results also indicate that the inclusion
of carbazole-2,7-diyl units into rigid-rod organometallic polymers
should enhance electronic transport along the chains
New Multi-Ferrocenyl- and Multi-Ferricenyl- Materials via Coordination-Driven Self-Assembly and via Charge-Driven Electro-Crystallization
Three
new tetra-ferrocenylethynylpyridinyl copper complexes, L<sub>4</sub>(CuI)<sub>4</sub> (<b>3</b>), L<sub>4</sub>(CuBr)<sub>2</sub> (<b>4</b>), and L<sub>4</sub>(CuCl)<sub>2</sub> (<b>5</b>) have been prepared from the reaction of ferrocenylÂethynylÂpyridine
(L)Â(<b>2</b>) with copper halides CuX (with X = I<sup>–</sup>, Br<sup>–</sup>, Cl<sup>–</sup>).The ligand <b>2</b> and the complexes <b>3</b>–<b>5</b> have
been fully characterized by spectroscopic methods. The structures
of <b>2</b>–<b>4</b> have been confirmed by single-crystal
X-ray crystallography. <b>2</b> forms a dimer in the crystalline-state
through C–H··N hydrogen bonds. <b>4</b> and <b>5</b> are dimers and <b>3</b> a tetramer, in all cases linked
through Cu–X··Cu bridging interactions. Cyclic voltammetry
in dichloroethane showed chemically reversible multiferrocenyl oxidation
signals with evidence for product electro-crystallization. The oxidation
products were isolated by electrodeposition onto a Pt disc electrode
and investigated by scanning electron microscopy which confirmed the
spontaneous formation of crystalline oxidation products with distinctive
morphologies. Energy dispersive X-ray elemental analysis shows the
presence of hexafluorophosphate (counterion) with the P:Fe ratio of
1:1, 0.5:1, and 1:1 for the electrocrystallized products <b>3</b>, <b>4</b>, and <b>5</b>, respectively, suggesting the
formulas [<b>3</b>]<sup>4+</sup>(PF<sub>6</sub><sup>–</sup>)<sub>4</sub>, [<b>4</b>]<sup>2+</sup>(PF<sub>6</sub><sup>–</sup>)<sub>2</sub>, and [<b>5</b>]<sup>4+</sup>(PF<sub>6</sub><sup>–</sup>)<sub>4</sub> for the electro-crystallized products
Long-Range Intramolecular Electronic Communication in Bis(ferrocenylethynyl) Complexes Incorporating Conjugated Heterocyclic Spacers: Synthesis, Crystallography, and Electrochemistry
A new series of bisÂ(ferrocenylethynyl)
complexes, <b>3</b>–<b>7</b>, and a monoÂ(ferrocenylethynyl)
complex, <b>8</b>, have been synthesized incorporating conjugated
heterocyclic spacer groups, with the ethynyl group facilitating an
effective long-range intramolecular interaction. The complexes were
characterized by NMR, IR, and UV–vis spectroscopy as well as
X-ray crystallography. The redox properties of these complexes were
investigated using cyclic voltammetry and spectroelectrochemistry.
Although there is a large separation of ∼14 Å between
the two redox centers, Δ<i>E</i><sub>1/2</sub> values
in this series of complexes ranged from 50 to 110 mV. The appearance
of intervalance charge-transfer bands in the UV–vis–near-IR
region for the monocationic complexes further confirmed effective
intramolecular electronic communication. Computational studies are
presented that show the degree of delocalization across the Fc–CC–CC–Fc
(Fc = C<sub>5</sub>H<sub>5</sub>FeC<sub>5</sub>H<sub>4</sub>) highest
occupied molecular orbital