13 research outputs found
Structural and Photophysical Study on Alkynyl Cyclometalated Pt<sub>2</sub>Pb<sub>2</sub> and Pt<sub>2</sub>Pb Clusters
Neutralization reactions
of (NBu<sub>4</sub>)Ā[PtĀ(bzq)Ā(Cī¼CR)<sub>2</sub>] (bzq = 7,8-benzoquinolinyl)
with [PbĀ(HBpz<sub>3</sub>)]ĀCl
(pz = pyrazolyl) afford tetranuclear neutral Pt<sub>2</sub>Pb<sub>2</sub> derivatives [{PtĀ(bzq)Ā(Cī¼CR)<sub>2</sub>}Ā{PbĀ(HBpz<sub>3</sub>)}]<sub>2</sub> (R = Ph, <b>1</b>; C<sub>6</sub>H<sub>4</sub>OMe-3, <b>2</b>) or the anionic trinuclear Pt<sub>2</sub>Pb cluster (NBu<sub>4</sub>)Ā[{PtĀ(bzq)Ā(Cī¼CC<sub>6</sub>H<sub>4</sub>CF<sub>3</sub>-4)<sub>2</sub>}<sub>2</sub>Ā{PbĀ(HBpz<sub>3</sub>)}], <b>3</b>, stabilized by PtāPb and Pb<sup>II</sup>Ā·Ā·Ā·Ī·<sup>2</sup>-(Cī¼CR) bonding interactions in the solid state, as
confirmed by X-ray crystallography. The variable-temperature <sup>1</sup>H NMR spectra of <b>3</b> confirm the existence of a
dynamic equilibrium that averages the āPtĀ(bzq)Ā(Cī¼CC<sub>6</sub>H<sub>4</sub>CF<sub>3</sub>-4)<sub>2</sub>ā groups
in solution. 1D <sup>1</sup>H PGSE-NMR, 2D DOSY, and <sup>1</sup>H
variable-temperature NMR experiments for the tetranuclear clusters <b>1</b> and <b>2</b> indicate that in solution these dimers
generate mainly binuclear [{PtĀ(bzq)Ā(Cī¼CR)<sub>2</sub>}Ā{PbĀ(HBpz<sub>3</sub>)}] units by cleavage of the Pb<sup>II</sup>Ā·Ā·Ā·Ī·<sup>2</sup>-(Cī¼CR) interactions. All clusters exhibit phosphorescent
emission in rigid media (solid, glasses) and <b>3</b> also in
CH<sub>2</sub>Cl<sub>2</sub> solution. The emission maxima of <b>1</b> and <b>2</b> are slightly blue-shifted in relation
to the precursors, being assigned to a mixed <sup>3</sup>MLCT/<sup>3</sup>LC (L = bzq) excited state, perturbed by the PtāPb
bond. However, the emission maximum of <b>3</b> coincides with
that of its precursor, indicating little or no involvement of the
PtāPb bonds in the emissive state
Synthesis, Structural, and Photophysical Studies of Phenylquinoline and Phenylquinolinyl Alkynyl Based Pt(II) Complexes
We present the synthesis, characterization, and photophysical properties
of two series of alkynylāplatinumĀ(II) complexes containing
the phenylquinoline (Hpq) or the cyclometalated phenylquinolinyl (pq)
ligand. Unusual monoanionic complexes (NBu<sub>4</sub>)Ā[PtĀ(Cī¼CR)<sub>3</sub>Ā(Hpq)] (R = Tol <b>1</b>, C<sub>6</sub>H<sub>4</sub>OMe-3 <b>2</b>, C<sub>6</sub>H<sub>4</sub>CF<sub>3</sub>-4 <b>3</b>) were generated in moderate yield by treatment of [PtĀ(pq)Ā(Ī¼-Cl)]<sub>2</sub> with an excess of LiCī¼CR (1:8), followed by subsequent
treatment with NBu<sub>4</sub> in <i>i</i>PrOH. However, a similar reaction with LiCī¼C<i><sup>t</sup></i>Bu evolves with formation of [PtĀ(pq)Ā(Ī¼ā<i>ĪŗC</i><sup>Ī±</sup>:āĪ·<sup>2</sup>-Cī¼C<sup><i>t</i></sup>Bu)]<sub>2</sub> <b>4</b>. Related
dimers [PtĀ(pq)Ā(Ī¼ā<i>ĪŗC</i><sup>Ī±</sup>:āĪ·<sup>2</sup>-Cī¼CR)]<sub>2</sub> (R = Tol <b>5</b>, C<sub>6</sub>H<sub>4</sub>OMe-3 <b>6</b>, C<sub>6</sub>H<sub>4</sub>CF<sub>3</sub>-4 <b>7</b>) were
successfully prepared by modification of the reaction conditions.
Single-crystal studies were performed on <b>2</b>, <b>4</b>, and <b>5</b>, revealing the presence of <i>intramolecular</i> (HĀ·Ā·Ā·Pt and HĀ·Ā·Ā·Cī¼C) and <i>intermolecular</i> O<sub>methoxy</sub>Ā·Ā·Ā·H<sub>Hpq</sub> contacts in <b>2</b> and the formation of butterfly
structures in <b>4</b> and <b>5</b>. In the <i><sup>t</sup></i>Bu derivative <b>4</b>, a shorter intramolecular
PtĀ·Ā·Ā·Pt separation was found [3.0936(3) Ć
in <b>4</b> vs 3.2109(3) Ć
in <b>5</b>], which is related
to the nature of Ī·<sup>2</sup>-alkynyl linkages (Ī·<sup>2</sup>-<i>asymmetrical</i> in <b>4</b> vs Ī·<sup>2</sup>-<i>symmetrical</i> in <b>5</b>). Anionic <b>1</b>ā<b>3</b> display bright emissions in rigid
media (solid, glass) with resolved side vibronic bands at 77 K. The
energy of the emissions (supported by computational studies on <b>2</b>) allows us to ascribe these emissions primarily to a mixed
alkynylāmetal to the phenylquinoline <sup>3</sup>[(Lā²
+ M)ĀLCT] excited state, being perturbed in <b>2</b> (solid)
by the <i>intermolecular</i> O<sub>methoxy</sub>Ā·Ā·Ā·H<sub>Hpq</sub> contacts. Whereas diplatinum complexes <b>5</b>ā<b>7</b> have no visible emission at 298 K in the solid state, <b>4</b> shows a structureless band (578 nm), which is significantly
red-shifted at 77 K (595 nm). Theoretical studies suggest a notable
distortion in the excited state in relation to S<sub>0</sub> and identify
the emission within the dimetallacycle Pt<sub>2</sub>(Cī¼C)<sub>2</sub> with alkynyl to pq charge-transfer <sup>3</sup>[(MM + Lā²)ĀLCT]
[with minor <sup>3</sup>IL (pq) contribution], whereas, in <b>5</b>, the emission is tentatively ascribed to a mixture of <sup>3</sup>Lā²LCT with minor <sup>3</sup>MMLCT character. The emission
profiles observed in glassy solution for all <b>4</b>ā<b>7</b> complexes (556ā562 nm, CH<sub>2</sub>Cl<sub>2</sub>) and in the solid state for <b>6</b>ā<b>7</b> are consistent with those exhibited by mononuclear related chromophores <sup>3</sup>[(Lā² + M)ĀLCT] (Lā² = Cī¼CR, L = pq), suggesting
negligible contribution of the PtĀ·Ā·Ā·Pt interaction
Synthesis, Structural, and Photophysical Studies of Phenylquinoline and Phenylquinolinyl Alkynyl Based Pt(II) Complexes
We present the synthesis, characterization, and photophysical properties
of two series of alkynylāplatinumĀ(II) complexes containing
the phenylquinoline (Hpq) or the cyclometalated phenylquinolinyl (pq)
ligand. Unusual monoanionic complexes (NBu<sub>4</sub>)Ā[PtĀ(Cī¼CR)<sub>3</sub>Ā(Hpq)] (R = Tol <b>1</b>, C<sub>6</sub>H<sub>4</sub>OMe-3 <b>2</b>, C<sub>6</sub>H<sub>4</sub>CF<sub>3</sub>-4 <b>3</b>) were generated in moderate yield by treatment of [PtĀ(pq)Ā(Ī¼-Cl)]<sub>2</sub> with an excess of LiCī¼CR (1:8), followed by subsequent
treatment with NBu<sub>4</sub> in <i>i</i>PrOH. However, a similar reaction with LiCī¼C<i><sup>t</sup></i>Bu evolves with formation of [PtĀ(pq)Ā(Ī¼ā<i>ĪŗC</i><sup>Ī±</sup>:āĪ·<sup>2</sup>-Cī¼C<sup><i>t</i></sup>Bu)]<sub>2</sub> <b>4</b>. Related
dimers [PtĀ(pq)Ā(Ī¼ā<i>ĪŗC</i><sup>Ī±</sup>:āĪ·<sup>2</sup>-Cī¼CR)]<sub>2</sub> (R = Tol <b>5</b>, C<sub>6</sub>H<sub>4</sub>OMe-3 <b>6</b>, C<sub>6</sub>H<sub>4</sub>CF<sub>3</sub>-4 <b>7</b>) were
successfully prepared by modification of the reaction conditions.
Single-crystal studies were performed on <b>2</b>, <b>4</b>, and <b>5</b>, revealing the presence of <i>intramolecular</i> (HĀ·Ā·Ā·Pt and HĀ·Ā·Ā·Cī¼C) and <i>intermolecular</i> O<sub>methoxy</sub>Ā·Ā·Ā·H<sub>Hpq</sub> contacts in <b>2</b> and the formation of butterfly
structures in <b>4</b> and <b>5</b>. In the <i><sup>t</sup></i>Bu derivative <b>4</b>, a shorter intramolecular
PtĀ·Ā·Ā·Pt separation was found [3.0936(3) Ć
in <b>4</b> vs 3.2109(3) Ć
in <b>5</b>], which is related
to the nature of Ī·<sup>2</sup>-alkynyl linkages (Ī·<sup>2</sup>-<i>asymmetrical</i> in <b>4</b> vs Ī·<sup>2</sup>-<i>symmetrical</i> in <b>5</b>). Anionic <b>1</b>ā<b>3</b> display bright emissions in rigid
media (solid, glass) with resolved side vibronic bands at 77 K. The
energy of the emissions (supported by computational studies on <b>2</b>) allows us to ascribe these emissions primarily to a mixed
alkynylāmetal to the phenylquinoline <sup>3</sup>[(Lā²
+ M)ĀLCT] excited state, being perturbed in <b>2</b> (solid)
by the <i>intermolecular</i> O<sub>methoxy</sub>Ā·Ā·Ā·H<sub>Hpq</sub> contacts. Whereas diplatinum complexes <b>5</b>ā<b>7</b> have no visible emission at 298 K in the solid state, <b>4</b> shows a structureless band (578 nm), which is significantly
red-shifted at 77 K (595 nm). Theoretical studies suggest a notable
distortion in the excited state in relation to S<sub>0</sub> and identify
the emission within the dimetallacycle Pt<sub>2</sub>(Cī¼C)<sub>2</sub> with alkynyl to pq charge-transfer <sup>3</sup>[(MM + Lā²)ĀLCT]
[with minor <sup>3</sup>IL (pq) contribution], whereas, in <b>5</b>, the emission is tentatively ascribed to a mixture of <sup>3</sup>Lā²LCT with minor <sup>3</sup>MMLCT character. The emission
profiles observed in glassy solution for all <b>4</b>ā<b>7</b> complexes (556ā562 nm, CH<sub>2</sub>Cl<sub>2</sub>) and in the solid state for <b>6</b>ā<b>7</b> are consistent with those exhibited by mononuclear related chromophores <sup>3</sup>[(Lā² + M)ĀLCT] (Lā² = Cī¼CR, L = pq), suggesting
negligible contribution of the PtĀ·Ā·Ā·Pt interaction
Facile Metalation of Hbzq by [<i>cis</i>-Pt(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>(thf)<sub>2</sub>]: A Route to a Pentafluorophenyl Benzoquinolate Solvate Complex That Easily Coordinates Terminal Alkynes. Spectroscopic and Optical Properties
A new neutral cyclometalated platinumĀ(II) solvate complex
[<i>cis</i>-PtĀ(bzq)Ā(C<sub>6</sub>F<sub>5</sub>)Ā(acetone)]
(<b>1</b>) has been prepared by easy CāH activation of
7,8-benzoĀ[<i>h</i>]Āquinoline on the coordination sphere
of [<i>cis</i>-PtĀ(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>(thf)<sub>2</sub>] (thf
= tetrahydrofuran). The study of the reaction pathway has led us to
the preparation of the bisĀ(Hbzq) product [<i>cis</i>-PtĀ(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>(Hbzq)<sub>2</sub>] (<b>2</b>) and the benzoquinolineābenzoquinolate derivative [PtĀ(bzq)Ā(C<sub>6</sub>F<sub>5</sub>)Ā(Hbzq)] (<b>3</b>). This latter complex
has been characterized by X-ray diffraction, showing the occurrence
of ĻĀ·Ā·Ā·Ļ intermolecular stacking interactions
associated to the deprotonated bzq units. The acetone molecule in
[<i>cis</i>-PtĀ(bzq)Ā(C<sub>6</sub>F<sub>5</sub>)Ā(acetone)]
can be easily displaced by alkynes, allowing the synthesis of the
first reported Ī·<sup>2</sup>-alkyne-cycloplatinate complexes
[PtĀ(bzq)Ā(C<sub>6</sub>F<sub>5</sub>)Ā(Ī·<sup>2</sup>-RCī¼CRā²)]
(R = H, Rā² = Ph <b>4</b>, <sup>t</sup>Bu <b>5</b>, Fc <b>6</b>; R = Rā² = Ph <b>7</b>), which have
been fully characterized spectroscopically and by DFT studies. These
alkyne complexes are only moderately stable in solution, and all attempts
to obtain crystals suitable for X-ray diffraction were fruitless.
Nevertheless, in the case of the ferrocenyl derivative, crystals of
complex [PtĀ(Īŗ<i>N</i>:Ī·<sup>2</sup>-bzq-Cā”CFc)Ā(C<sub>6</sub>F<sub>5</sub>)Ā(Ī¼-Īŗ<i>C</i><sup>Ī±</sup>:Ī·<sup>2</sup>-Cā”CFc)ĀPtĀ(bzq)Ā(C<sub>6</sub>F<sub>5</sub>)] (<b>8</b>), containing an unusual alkynyl-functionalized
benzoquinoline chelate ligand, were systematically obtained. All complexes
(except those containing the ferrocenyl fragment) present emissive
properties in solution and solid state (77 K), related, in general,
with intraligand (bzq) excited states with some mixing <sup>3</sup>MLCT character, as supported by theoretical calculations. In solid
state at room temperature, aggregation induced emission (AIE) is observed
likely generated by intermolecular ĻĀ·Ā·Ā·Ļ
stacking, as supporting by DFT calculations on <b>3</b><sub><b>2</b></sub>. Interestingly, both types of excited states
(<sup>3</sup>IL/<sup>3</sup>MLCT and AIE) seem to be close in energy
in complexes <b>1</b> and <b>3</b>, which show a significant
luminescent thermochromism (green 77 K to orange 298 K)
Facile Metalation of Hbzq by [<i>cis</i>-Pt(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>(thf)<sub>2</sub>]: A Route to a Pentafluorophenyl Benzoquinolate Solvate Complex That Easily Coordinates Terminal Alkynes. Spectroscopic and Optical Properties
A new neutral cyclometalated platinumĀ(II) solvate complex
[<i>cis</i>-PtĀ(bzq)Ā(C<sub>6</sub>F<sub>5</sub>)Ā(acetone)]
(<b>1</b>) has been prepared by easy CāH activation of
7,8-benzoĀ[<i>h</i>]Āquinoline on the coordination sphere
of [<i>cis</i>-PtĀ(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>(thf)<sub>2</sub>] (thf
= tetrahydrofuran). The study of the reaction pathway has led us to
the preparation of the bisĀ(Hbzq) product [<i>cis</i>-PtĀ(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>(Hbzq)<sub>2</sub>] (<b>2</b>) and the benzoquinolineābenzoquinolate derivative [PtĀ(bzq)Ā(C<sub>6</sub>F<sub>5</sub>)Ā(Hbzq)] (<b>3</b>). This latter complex
has been characterized by X-ray diffraction, showing the occurrence
of ĻĀ·Ā·Ā·Ļ intermolecular stacking interactions
associated to the deprotonated bzq units. The acetone molecule in
[<i>cis</i>-PtĀ(bzq)Ā(C<sub>6</sub>F<sub>5</sub>)Ā(acetone)]
can be easily displaced by alkynes, allowing the synthesis of the
first reported Ī·<sup>2</sup>-alkyne-cycloplatinate complexes
[PtĀ(bzq)Ā(C<sub>6</sub>F<sub>5</sub>)Ā(Ī·<sup>2</sup>-RCī¼CRā²)]
(R = H, Rā² = Ph <b>4</b>, <sup>t</sup>Bu <b>5</b>, Fc <b>6</b>; R = Rā² = Ph <b>7</b>), which have
been fully characterized spectroscopically and by DFT studies. These
alkyne complexes are only moderately stable in solution, and all attempts
to obtain crystals suitable for X-ray diffraction were fruitless.
Nevertheless, in the case of the ferrocenyl derivative, crystals of
complex [PtĀ(Īŗ<i>N</i>:Ī·<sup>2</sup>-bzq-Cā”CFc)Ā(C<sub>6</sub>F<sub>5</sub>)Ā(Ī¼-Īŗ<i>C</i><sup>Ī±</sup>:Ī·<sup>2</sup>-Cā”CFc)ĀPtĀ(bzq)Ā(C<sub>6</sub>F<sub>5</sub>)] (<b>8</b>), containing an unusual alkynyl-functionalized
benzoquinoline chelate ligand, were systematically obtained. All complexes
(except those containing the ferrocenyl fragment) present emissive
properties in solution and solid state (77 K), related, in general,
with intraligand (bzq) excited states with some mixing <sup>3</sup>MLCT character, as supported by theoretical calculations. In solid
state at room temperature, aggregation induced emission (AIE) is observed
likely generated by intermolecular ĻĀ·Ā·Ā·Ļ
stacking, as supporting by DFT calculations on <b>3</b><sub><b>2</b></sub>. Interestingly, both types of excited states
(<sup>3</sup>IL/<sup>3</sup>MLCT and AIE) seem to be close in energy
in complexes <b>1</b> and <b>3</b>, which show a significant
luminescent thermochromism (green 77 K to orange 298 K)
Phenylbenzothiazole-Based Platinum(II) and Diplatinum(II) and (III) Complexes with Pyrazolate Groups: Optical Properties and Photocatalysis
Based on 2-phenylbenzothiazole (pbt) and 2-(4-dimethylaminophenyl)benzothiazole
(Me2N-pbt), mononuclear [Pt(pbt)(Rā²2-pzH)2]PF6 (Rā²2-pzH = pzH 1a, 3,5-Me2pzH 1b, 3,5-iPr2pzH 1c) and diplatinum (PtIIāPtII) [Pt(pbt)(Ī¼-Rā²2pz)]2 (Rā²2-pz = pz 2a, 3,5-Me2pz 2b, 3,5-iPr2pz 2c) and [Pt(Me2N-pbt)(Ī¼-pz)]2 (3a) complexes
have been prepared. In the presence of sunlight, 2a and 3a evolve, in CHCl3 solution, to form the PtIIIāPtIII complexes [Pt(R-pbt)(Ī¼-pz)Cl]2 (R = H 4a, NMe2 5a).
Experimental and computational studies reveal the negligible influence
of the pyrazole or pyrazolate ligands on the optical properties of 1aāc and 2a,b, which exhibit a typical 3IL/3MLCT emission,
whereas in 2c the emission has some 3MMLCT
contribution. 3a displays unusual dual, fluorescence
(1ILCT or 1MLCT/1LC), and phosphorescence
(3ILCT) emissions depending on the excitation wavelength.
The phosphorescence is lost in aerated solutions due to sensitization
of 3O2 and formation of 1O2, whose determined quantum yield is also wavelength dependent. The
phosphorescence can be reversibly photoinduced (365 nm, ā¼ 15
min) in oxygenated THF and DMSO solutions. In 4a and 5a, the lowest electronic transitions (S1āS3) have mixed characters (LMMCT/LXCT/LāXCT 4a and LMMCT/LXCT/ILCT 5a) and they are weakly emissive
in rigid media. The 1O2 generation property
of complex 3a is successfully used for the photooxidation
of p-bromothioanisol showing its potential application
toward photocatalysis
An Extended Chain and Trinuclear Complexes Based on Pt(II)āM (M = Tl(I), Pb(II)) Bonds: Contrasting Photophysical Behavior
The
syntheses and structural characterizations of a PtāTl chain
[{PtĀ(bzq)Ā(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>}ĀTlĀ(Me<sub>2</sub>CO)]<sub><i>n</i></sub> <b>1</b> and two trinuclear
Pt<sub>2</sub>M clusters (NBu<sub>4</sub>)Ā[{PtĀ(bzq)Ā(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>}<sub>2</sub>Tl] <b>2</b> and [{PtĀ(bzq)Ā(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>}<sub>2</sub>Pb] <b>3</b> (bzq
= 7,8-benzoquinolinyl), stabilized by donorāacceptor Pt ā
M bonds, are reported. The one-dimensional heterometallic chain <b>1</b> is formed by alternate āPtĀ(bzq)Ā(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>ā and āTlĀ(Me<sub>2</sub>CO)ā
fragments, with PtāTl bond separations in the range of 2.961(1)ā3.067(1)
Ć
. The isoelectronic trinuclear complexes <b>2</b> (which
crystallizes in three forms, namely, <b>2a</b>, <b>2b</b>, and <b>2c</b>) and <b>3</b> present a sandwich structure
in which the TlĀ(I) or PbĀ(II) is located between two āPtĀ(bzq)Ā(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>ā subunits. NMR studies suggest
equilibria in solution implying cleavage and reformation of PtāM
bonds. The lowest-lying absorption band in the UVāvis spectra
in CH<sub>2</sub>Cl<sub>2</sub> and tetrahydrofuran (THF) of <b>1</b>, associated with <sup>1</sup>MLCT/<sup>1</sup>Lā²LCT <sup>1</sup>[5d<sub>Ļ</sub>(Pt) ā Ļ*Ā(bzq)]/<sup>1</sup>[(C<sub>6</sub>F<sub>5</sub>) ā bzq], displays a blue shift
in relation to the precursor, suggesting the cleavage of the chain
maintaining bimetallic PtāTl fragments in solution, also supported
by NMR spectroscopy. In <b>2</b> and <b>3</b>, it shows
a blue shift in THF and a red shift in CH<sub>2</sub>Cl<sub>2</sub>, supporting a more extensive cleavage of the PtāM bonds in
THF solutions than in CH<sub>2</sub>Cl<sub>2</sub>, where the trinuclear
entities are predominant. The PtāTl chain <b>1</b> displays
in solid state a bright orange-red emission ascribed to <sup>3</sup>MMā²CT (Mā² = Tl). It exhibits remarkable and fast reversible
vapochromic and vapoluminescent response to donor vapors (THF and
Et<sub>2</sub>O), related to the coordination/decoordination of the
guest molecule to the TlĀ(I) ion, and mechanochromic behavior, associated
with the shortening of the intermetallic PtāTl separations
in the chain induced by grinding. In frozen solutions (THF, acetone,
and CH<sub>2</sub>Cl<sub>2</sub>) <b>1</b> shows interesting
luminescence thermochromism with emissions strongly dependent on the
solvent, concentration, and excitation wavelengths. The Pt<sub>2</sub>Tl complex <b>2</b> shows an emission close to <b>1</b>, ascribed to charge transfer from the platinum fragment to the thallium
[<sup>3</sup>(L+Lā²)ĀMMā²CT]. <b>2</b> also shows
vapoluminescent behavior in the presence of vapors of Me<sub>2</sub>CO, THF, and Et<sub>2</sub>O, although smaller and slower than those
of <b>1</b>. The trinuclear neutral complex Pt<sub>2</sub>Pb <b>3</b> displays a blue-shift emission band, tentatively assigned
to admixture of <sup>3</sup>MMā²CT <sup>3</sup>[PtĀ(d) ā
PbĀ(sp)] with some metal-mediated intraligand (<sup>3</sup>ĻĻ/<sup>3</sup>ILCT) contribution. In contrast to <b>1</b> and <b>2</b>, <b>3</b> does not show vapoluminescent behavior
Synthesis, Characterization, and Properties of Doubly Alkynyl Bridging Dinuclear Cyclometalated Iridium(III) Complexes
BisĀ(cyclometalated) diiridium complexes
[IrĀ(ppy)<sub>2</sub>(Ī¼āĪŗ<i>C</i><sup>Ī±</sup>:Ī·<sup>2</sup>-Cī¼CR)]<sub>2</sub> (R =
Tol <b>1</b>, C<sub>6</sub>H<sub>4</sub>OMe-4 <b>2</b>, 1-Np <b>3</b>, SiMe<sub>3</sub> <b>4</b>, <sup><i>t</i></sup>Bu <b>5</b>), stabilized by a double
alkynyl bridging system, have been synthesized by alkynylation of
[IrĀ(ppy)<sub>2</sub>(Ī¼-Cl)]<sub>2</sub> with excess of the appropriate
LiCī¼CR (1:6 or 1:10 molar ratio). Complexes <b>1</b>ā<b>3</b> were alternatively generated by treatment of [IrĀ(ppy)<sub>2</sub>(MeCN)<sub>2</sub>]Ā(OTf) with 2.5 equiv of LiCī¼CR.
However, the related reaction with LiCī¼C<sup><i>t</i></sup>Bu evolves with the formation of mixtures from which the unexpected
dinuclear complex [IrĀ(ppy)<sub>2</sub>(Ī¼-CH<sub>2</sub>CN)]<sub>2</sub> <b>6</b> was crystallized, as confirmed by X-ray diffraction
studies. Complexes <b>1</b>ā<b>5</b> have been
characterized by NMR, IR, absorption and emission spectroscopies,
cyclic voltammetry, and mass spectrometric methods. Characterization
indicates that <b>1</b>ā<b>3</b> and <b>5</b> are obtained as a unique diastereoisomer (ĪĪ/ĪĪ),
whereas <b>4</b> gives the two diastereoisomers (ĪĪ
and ĪĪ/ĪĪ). Single crystals of [IrĀ(ppy)<sub>2</sub>(Ī¼-Cī¼CTol)]<sub>2</sub> <b>1</b> contains
the inversion related ĪĪ/ĪĪ isomers, and crystals
of <b>4</b> (chosen from a mixture of two different types of
crystals) consist of the <i>meso</i>-ĪĪ isomer.
Electrochemical studies showed the presence in <b>1</b>ā<b>3</b> and <b>5</b> of two consecutive one-electron-oxidation
Ir<sup>III</sup>/Ir<sup>IV</sup> processes, whereas <b>4</b> displayed only one irreversible oxidation peak. In degassed fluid
solutions, complexes <b>1</b>ā<b>5</b> are emissive
in the 505ā515 nm region with quantum yields higher (Ļ
= 0.007ā0.024) than that of the dichloro bridged precursor
(0.0037). The influence of the alkynyl substituent in the emissive
state at room and at low temperatures has been investigated. For the
naphthylacetylide derivative <b>3</b>, a clear switch from a
mixed charge transfer <sup>3</sup>MLCT/<sup>3</sup>Lā²LCT excited
state at 298 K (515 nm) to a characteristic long-lived low lying naphthalene
emission at low temperature (77 K) is observed. DFT and TD-DFT calculations
were performed on complexes <b>1</b> and <b>3</b> in the
ground and triplet states to gain insight into the structural, electronic,
and photophysical properties
Unexpected Formation of Ferrocenyl(vinyl)benzoquinoline Ligands by Oxidation of an Alkyne Benzoquinolate Platinum(II) Complex
Oxidation
of [PtĀ(bzq-Īŗ<i>N</i>,Īŗ<i>C</i><sup>10</sup>)Ā(C<sub>6</sub>F<sub>5</sub>)Ā(Ī·<sup>2</sup>-HCī¼CFc)]
(<b>1</b>) with PhICl<sub>2</sub> and I<sub>2</sub> affords
the unusual halideferrocenylĀ(vinyl)Ābenzoquinoline Pt<sup>II</sup> derivatives
[PtĀ{bzq-Īŗ<i>N</i>-Ī·<sup>2</sup>-CHī»CĀ(X)ĀFc}Ā(C<sub>6</sub>F<sub>5</sub>)ĀX] (X = Cl (<b>4a</b>), I (<b>4b</b>)), arising from CāX and CāC coupling processes, together
with small amounts of the corresponding Pt<sup>IV</sup> products [{PtĀ(bzq-Īŗ<i>N</i>,Īŗ<i>C</i><sup>10</sup>)Ā(C<sub>6</sub>F<sub>5</sub>)ĀXĀ(Ī¼-X)}<sub>2</sub>] (X = Cl (<b>5a</b>), I (<b>5b</b>)), respectively. Complexes <b>4</b> are very stable
but they undergo easy displacement reactions with PPh<sub>3</sub>,
yielding <i>trans</i>-[PtĀ(C<sub>6</sub>F<sub>5</sub>)ĀXĀ(PPh<sub>3</sub>)<sub>2</sub>] and the corresponding new functionalized (vinyl)Ābenzoquinoline
ligands [(<i>Z</i>)-bzq-CHī»CĀ(X)ĀFc] (X = Cl (<b>6a</b>), I (<b>6b</b>)). The dinuclear Pt<sup>IV</sup> derivatives <b>5</b> are alternatively obtained in high yield by oxidation of
the solvate [PtĀ(bzq-Īŗ<i>N</i>,Īŗ<i>C</i><sup>10</sup>)Ā(C<sub>6</sub>F<sub>5</sub>)Ā(CH<sub>3</sub>COCH<sub>3</sub>)] (<b>2</b>). Treatment of <b>5</b> with dmso
or direct oxidation of [PtĀ(bzq-Īŗ<i>N</i>,Īŗ<i>C</i><sup>10</sup>)Ā(C<sub>6</sub>F<sub>5</sub>)Ā(tht)] (<b>3</b>) provides mononuclear [PtĀ(bzq-Īŗ<i>N</i>,Īŗ<i>C</i><sup>10</sup>)Ā(C<sub>6</sub>F<sub>5</sub>)ĀX<sub>2</sub>(L)] (L = dmso (<b>7a</b>ā<b>c</b>), tht (<b>8a</b>ā<b>c</b>)) as a mixture of <i>cis</i> and <i>trans</i> isomers
Synthesis, Characterization, and Properties of Doubly Alkynyl Bridging Dinuclear Cyclometalated Iridium(III) Complexes
BisĀ(cyclometalated) diiridium complexes
[IrĀ(ppy)<sub>2</sub>(Ī¼āĪŗ<i>C</i><sup>Ī±</sup>:Ī·<sup>2</sup>-Cī¼CR)]<sub>2</sub> (R =
Tol <b>1</b>, C<sub>6</sub>H<sub>4</sub>OMe-4 <b>2</b>, 1-Np <b>3</b>, SiMe<sub>3</sub> <b>4</b>, <sup><i>t</i></sup>Bu <b>5</b>), stabilized by a double
alkynyl bridging system, have been synthesized by alkynylation of
[IrĀ(ppy)<sub>2</sub>(Ī¼-Cl)]<sub>2</sub> with excess of the appropriate
LiCī¼CR (1:6 or 1:10 molar ratio). Complexes <b>1</b>ā<b>3</b> were alternatively generated by treatment of [IrĀ(ppy)<sub>2</sub>(MeCN)<sub>2</sub>]Ā(OTf) with 2.5 equiv of LiCī¼CR.
However, the related reaction with LiCī¼C<sup><i>t</i></sup>Bu evolves with the formation of mixtures from which the unexpected
dinuclear complex [IrĀ(ppy)<sub>2</sub>(Ī¼-CH<sub>2</sub>CN)]<sub>2</sub> <b>6</b> was crystallized, as confirmed by X-ray diffraction
studies. Complexes <b>1</b>ā<b>5</b> have been
characterized by NMR, IR, absorption and emission spectroscopies,
cyclic voltammetry, and mass spectrometric methods. Characterization
indicates that <b>1</b>ā<b>3</b> and <b>5</b> are obtained as a unique diastereoisomer (ĪĪ/ĪĪ),
whereas <b>4</b> gives the two diastereoisomers (ĪĪ
and ĪĪ/ĪĪ). Single crystals of [IrĀ(ppy)<sub>2</sub>(Ī¼-Cī¼CTol)]<sub>2</sub> <b>1</b> contains
the inversion related ĪĪ/ĪĪ isomers, and crystals
of <b>4</b> (chosen from a mixture of two different types of
crystals) consist of the <i>meso</i>-ĪĪ isomer.
Electrochemical studies showed the presence in <b>1</b>ā<b>3</b> and <b>5</b> of two consecutive one-electron-oxidation
Ir<sup>III</sup>/Ir<sup>IV</sup> processes, whereas <b>4</b> displayed only one irreversible oxidation peak. In degassed fluid
solutions, complexes <b>1</b>ā<b>5</b> are emissive
in the 505ā515 nm region with quantum yields higher (Ļ
= 0.007ā0.024) than that of the dichloro bridged precursor
(0.0037). The influence of the alkynyl substituent in the emissive
state at room and at low temperatures has been investigated. For the
naphthylacetylide derivative <b>3</b>, a clear switch from a
mixed charge transfer <sup>3</sup>MLCT/<sup>3</sup>Lā²LCT excited
state at 298 K (515 nm) to a characteristic long-lived low lying naphthalene
emission at low temperature (77 K) is observed. DFT and TD-DFT calculations
were performed on complexes <b>1</b> and <b>3</b> in the
ground and triplet states to gain insight into the structural, electronic,
and photophysical properties