Syntheses, characterization, and photophysical properties of conjugated organometallic Pt-Acetylide/Zn (II) porphyrin-containing oligomers

Article abstract of DOI:10.1021/ic901421m

Two conjugated organometallic oligomers of the type (-C≡CPt(L) ₂C≡C(ZnP)-)_n, and model compounds [PhC≡ CPt(L)2C≡C(ZnP)C≡CPt(L)₂C≡CPh] with L = tri(n-butyl)-phosphine and ZnP = zinc(ll)(10,20-bis(Ar)porphyrine) (Ar = mesityl (Mes; P1 and M1) or 3,4,5-trihexadecyloxyphenyl (P2 and M2)) were synthesized and characterized (¹H and ³¹P NMR, HRMS, elemental analysis, IR, GPC, and TGA). GPC indicates that P1 and P2 exhibit respectively ~6 and ~3 units with a polydispersity of 1.4. M1 was also characterized by X-ray crystallography. The Pt- ? -Pt separation in M1 is 1.61 nm, which makes P1 ~ 9.6 nm long. The spectral measurements show that the absorption and photoluminescence spectra of M1, M2, P1, and P2 are remarkably red-shifted. For example, the low energy Q-band is observed at 677 ± 1 nm in comparison with their precursors HC≡C(ZnP)C≡CH, L1 and L2 (Ar=mesityl (Mes; L1) or 3,4,5-trihexadecyloxyphenyl (L2)), both at 298 and 77 K, for which the Q-band is observed at 622 nm. The photophysical parameters, fluorescence lifetimes (TF), and quantum yields (φ_F) show a slight decrease by a factor of 2 (at most 3) following the trend L1 ~L2>M1 ~M2>P1 ~ P2, a trend explained by a combination of the heavy atom effect and an increase in internal conversion rate due to the increase in oligomer dimension. This small variation of the photophysical data for materials of a few nm in dimension contrasts with the larger change in τ_P, phosphorescence lifetimes of the Pt-containing unit in the (-C₆H₄C=CPt(L) ₂C=C-CC₆H₄(ZnP)-)_n oligomers with n = 3, 6, and 9 reported earlier (Liu, L.; Fortin, D.; Harvey, P. D. Inorg. Chem. 2009, 48, 5891 -5900). In this later case, tP decreased by steps of an order of magnitude as n increased from 3 to 6 to 9. This decrease was explained by a T1 energy transfer from the Pt unit (donor) to MP (acceptor) in combination with an excitonic process (energy derealization). Because of the full conjugation in P1 and P2, these oligomers behave as distinct molecules, and no energy transfer occurs. These properties make these materials suitable candidates for photocell applications.

Full text of DOI:10.1021/ic901421m

2614 Inorg. Chem. 2010, 49, 2614–2623
DOI: 10.1021/ic901421m
Syntheses, Characterization, and Photophysical Properties of Conjugated
Organometallic Pt-Acetylide/Zn(II) Porphyrin-Containing Oligomers
Feng-Lei Jiang, Daniel Fortin, and Pierre D. Harvey*
ꢀ
ꢀ
Departement de Chimie, Universite de Sherbrooke, PQ, Canada J1K 2R1
Received July 21, 2009
Two conjugated organometallic oligomers of the type (-CtCPt(L)2CtC(ZnP)-)n and model compounds [PhCt
CPt(L)2CtC(ZnP)CtCPt(L)2CtCPh] with L = tri(n-butyl)-phosphine and ZnP = zinc(II)(10,20-bis(Ar)porphyrine)
(Ar = mesityl (Mes; P1 and M1) or 3,4,5-trihexadecyloxyphenyl (P2 and M2)) were synthesized and characterized
(1H and 31P NMR, HRMS, elemental analysis, IR, GPC, and TGA). GPC indicates that P1 and P2 exhibit respectively
∼6 and ∼3 units with a polydispersity of 1.4. M1 was also characterized by X-ray crystallography. The Pt Pt
3 3 3
separation in M1 is 1.61 nm, which makes P1 ∼ 9.6 nm long. The spectral measurements show that the absorption and
photoluminescence spectra of M1, M2, P1, and P2 are remarkably red-shifted. For example, the low energy Q-band is
observed at 677 ( 1 nm in comparison with their precursors HCtC(ZnP)CtCH, L1 and L2 (Ar=mesityl (Mes; L1) or
3,4,5-trihexadecyloxyphenyl (L2)), both at 298 and 77 K, for which the Q-band is observed at 622 nm. The
photophysical parameters, fluorescence lifetimes (τF), and quantum yields (ΦF) show a slight decrease by a factor of
2 (at most 3) following the trend L1 ∼ L2>M1 ∼ M2>P1 ∼ P2, a trend explained by a combination of the heavy atom
effect and an increase in internal conversion rate due to the increase in oligomer dimension. This small variation of the
photophysical data for materials of a few nm in dimension contrasts with the larger change in τP, phosphorescence
lifetimes of the Pt-containing unit in the (-C6H4CtCPt(L)2CtC-CC6H4(ZnP)-)n oligomers with n = 3, 6, and 9
reported earlier (Liu, L.; Fortin, D.; Harvey, P. D. Inorg. Chem. 2009, 48, 5891-5900). In this later case, τP decreased
by steps of an order of magnitude as n increased from 3 to 6 to 9. This decrease was explained by a T1 energy transfer
from the Pt unit (donor) to MP (acceptor) in combination with an excitonic process (energy delocalization). Because of
the full conjugation in P1 and P2, these oligomers behave as distinct molecules, and no energy transfer occurs. These
properties make these materials suitable candidates for photocell applications.
Introduction
for LEDs. The ultimate efficiency of LEDs is largely con-
trolled by the fraction of triplet states generated or harvested
since spin statistics suggest a ratio of 3:1 for the generation of
a nonemissive triplet to emissive singlet exciton.2 Recent
progress has shown that metal-containing complexes should,
in principle, be superior to fluorescent substrates for small-
molecule organic LED applications.1c,2
The photovoltaic application of metallopolyynes has been
largely hampered by their wide bandgaps (Eg), and most of the
Pt(II) polyynes compare unfavorably with those of some
conjugated organic polymers comprising alternating electron
donor and acceptor units.3 Hence, new synthetic strategies for
creating metallopolyynes of low Eg would be desirable. Accord-
ing to the energy gap law for triplet emission, the nonradiative
decay rate from the triplet state increases exponentially with the
decreasing triplet-singlet energy gap (ΔES-T).4 A concise
In recent years, great attention was paid to the metallo-
polyyne polymers expected for applications in optoelectro-
nics such as light-emitting diodes (LEDs) and photovoltaic
cells.1 Indeed, the incorporation of a transition metal into
macromolecular organic scaffolds can lead to hybridization
of the electronic, optical, and magnetic properties of metal
complexes with the solubility and processability of carbon-
based polymers. Researchers focused primarily on transition
metal, notably Pt(II), acetylide oligoynes and polyynes con-
taining repeated units like trans-[-M(L)2CtC(R)CtC-]n,
where M is inserted in the macromolecules, L is an auxiliary
ligand, and R is a spacer unit, most of the time an aromatic
residue. Owing to the spin-orbit coupling caused by the
presence of heavy metals, the spin-forbidden triplet emission
with a longer lifetime is partially allowed, which is advantageous
(2) Cleave, V.; Yahioglu, G.; Le Barny, P.; Friend, R. H.; Tessler, N. Adv.
Mater. 1999, 11, 285–288.
*To whom correspondence should be addressed. Tel: 1-819-821-7092.
Fax: 1-819-821-8017. E-mail: Pierre.harvey@usherbrooke.ca.
(1) (a) Wong, W.-Y. Dalton Trans. 2007, 4495–4510. (b) Wong, W.-Y.; Ho,
C.-L. Coord. Chem. Rev. 2006, 250, 2627-2690 and references therein.
(c) Wong, W.-Y.; Harvey, P. D. Macromol. Rapid Commun. 2010, in press.
(3) Roncali, J. Chem. Rev. 1997, 97, 173–206.
(4) Wilson, J. S.; Chawdhury, N.; Al-Mandhary, M. R. A.; Younus, M.;
€
Khan, S. M.; Raithby, P. R.; Kohler, A.; Friend, R. H. J. Am. Chem. Soc.
2001, 123, 9412–9417.
r
pubs.acs.org/IC
Published on Web 02/08/2010
2010 American Chemical Society

Article
Inorganic Chemistry, Vol. 49, No. 6, 2010 2615
Chart 1
consideration and a good compromise of the triplet photo-
physics and the associated Eg in the polymer are essential in the
design of highly efficient and wavelength-tunable luminescent
and photovoltaically active materials.
except for a report on a porphyrin oligomer bridged by bis-
(phosphine)platinum(II),9 in which the monomers are cat-
ionic with no definite chemical composition and the monomers
and oligomers are mainly investigated for their morphology
rather than photophysical properties.10 Besides the heavy
metal effect, insertion of Pt(II) in macromolecules also led to
a large conduction bandwidth with a d8 square-planar con-
figuration.11 In connection with this class of compounds and
polymers, we recently reported a series of well-defined short
oligomers containing the fragments [C6H4CtCPtL2Ct
CC6H4] (L = monophosphine) and metallophorphyrins
(MP; see compounds 1-6)12a as well as longer poly-dispersed
oligomers (see compounds 7 and 8, and polymers 9 and 10 in
Chart 1).12b
In these studies on alternating nonconjugated and partially
conjugated (A-B)n materials, the T1 energy transfer pro-
cesses between the [C6H4CtCPtL2CtCC6H4] spacer (donor
in black) and MP (acceptor in gray) as well as the S1 and T1
energy transfers between the MP (M=Pd, donor; M=Zn,
acceptor) were observed (Scheme 1). These results illustrated
that the spacer and the metalloporphyrin moieties act as
distinct chromophores. Moreover, the main conclusion is
that the rates for T1 energy transfers are slow (on the order of
104 s-1) but vary as the oligomer length gets longer.12b In fact,
in the series 8 and 10 (where n = 3, 6, 9), the rate increases
by an order of magnitude when n passes from 3 (104) to
6 (105) to 9 (106 s-1). This indicates that an excitonic process
Porphyrin monomers have a relatively low Eg with large
absorption coefficients due to their large π conjugation. Even
larger π conjugation in porphyrin oligomers and polymers
results in an even lower Eg and larger absorption coefficients
in the red-shifted Q-band.5 Many researchers focused on
porphyrin oligomers and polymers bridged by ethyne,5
butadiyne,6 phenylenevinylene,7 aryl acetylene,8 etc., which
were mostly studied for their nonlinear optical properties,6a-f
electron transfer,6g single molecule conductance with ultra
low attenuation,6h,i and functionalization and solubilization
of the carbon nanotubes.6j However, there are very few
conjugated porphyrin oligomers bridged by Pt(II) acetylides,
(5) Duncan, T. V.; Susumu, K.; Sinks, L. E.; Therien, M. J. J. Am. Chem.
Soc. 2006, 128, 9000–9001.
(6) (a) Anderson, H. L.; Martin, S. J.; Bradley, D. D. C. Angew. Chem.,
Int. Ed. Engl. 1994, 33, 655–657. (b) Taylor, P. N.; Huuskonen, J.; Rumbles, G.;
Aplin, R. T.; Williams, E.; Anderson, H. L. Chem. Commun. 1998, 909–910.
(c) Anderson, H. L. Chem. Commun. 1999, 2323–2330. (d) Kuebler, S. M.;
Denning, R. G.; Anderson, H. L. J. Am. Chem. Soc. 2000, 122, 339–347.
(e) Screen, T. E. O.; Thorne, J. R. G.; Denning, R. G.; Bucknall, D. G.; Anderson,
H. L. J. Mater. Chem. 2003, 13, 2796–2808. (f) Drobizhev, M.; Stepanenko, Y.;
Rebane, A.; Wilson, C. J.; Screen, T. E. O.; Anderson, H. L. J. Am. Chem. Soc.
2006, 128, 12432–12433. (g) Winters, M. U.; Dahlstedt, E.; Blades, H. E.; Wilson,
C. J.; Frampton, M. J.; Anderson, H. L.; Albinsson, B. J. Am. Chem. Soc. 2007,
129, 4291–4297. (h) Sedghi, G.; Sawada, K.; Esdaile, L. J.; Hoffmann, M.;
Anderson, H. L.; Bethell, D.; Haiss, W.; Higgins, S. J.; Nichols, R. J. J. Am.
Chem. Soc. 2008, 130, 8582–8583. (i) Meier, H. Angew. Chem., Int. Ed. 2009,
48, 3911–3913. (j) Adronov, A.; Cheng, F. Chem.;Eur. J. 2006, 12, 5053–5059.
(7) (a) Jiang, B.; Yang, S.-W.; Jones, W. E., Jr. Chem. Mater. 1997, 9,
2031–2034. (b) Jiang, B.; Jones, W. E., Jr. Macromolecules 1997, 30, 5575–
5581.
(9) Ferri, A.; Polzonetti, G.; Licoccia, S.; Paolesse, R.; Favretto, D.;
Traldi, P.; Russo, M. V. J. Chem. Soc., Dalton Trans. 1998, 4063–4069.
(10) (a) Amato, M. E.; Licciardello, A.; Torrisi, V.; Ugo, L.; Venditti, I.;
Russo, M. V. Mater. Sci. Eng., C 2009, 29, 1010–1017. (b) Fratoddi, I.;
Battocchio, C.; Amato, R. D.; Di Egidio, G. P.; Ugo, L.; Polzonetti, G.; Russo,
M. V. Mater. Sci. Eng., C 2003, 23, 867–871.
(11) Flapper, G.; Kertesz, M. Inorg. Chem. 1993, 32, 732–740.
(12) (a) Bellows, D.; Aly, S. A.; Gros, C. P.; Ojaimi, M. E.; Barbe, J.-M.;
Guilard, R.; Harvey, P. D. Inorg. Chem. 2009, 48, 7613–7629. (b) Liu, L.;
Fortin, D.; Harvey, P. D. Inorg. Chem. 2009, 48, 5891–5900.
(8) (a) Jiang, B.; Yang, S.-W.; Barbini, D. C.; Jones, W. E., Jr. Chem.
Commun. 1998, 213–214. (b) Li, B.; Fu, Y.; Han, Y.; Bo, Z. Macromol. Rapid
Commun. 2006, 27, 1355–1361. (c) Screen, T. E. O.; Lawton, K. B.; Wilson,
G. S.; Dolney, N.; Ispasoiu, R.; Goodson, T., III; Martin, S. J.; Bradley, D. D. C.;
Anderson, H. L. J. Mater. Chem. 2001, 11, 312–320.

2616 Inorganic Chemistry, Vol. 49, No. 6, 2010
Jiang et al.
Scheme 1. Non-Radiative Energy Delocalization Processes in Pt-Acetylides/Porphyrin Oligomers
Chart 2
(i.e., energy delocalization) takes place along the backbone of
the oligomers when the number of acceptor units increases
(lesser probability of back energy transfer), hence accelera-
ting the T1 energy transfer between the donor and the
acceptor. Nonetheless, the rate is still slow. The next question
is, what does it take to accelerate the rates? One possible
answer is to render the (A-B)n polymers fully conjugated, so
the electronic communication between the chromophores
A and B is improved with respect to the previous systems.
Then, the next obvious question is, what is the role of the
oligomer length in the photophysical properties when the
system is totally conjugated?
We now wish to report herein the synthesis, characteri-
zation, photophysical properties, density functional the-
ory (DFT), and time dependent density functional theory
(TDDFT) analyses of porphyrin monomers (as model
compounds) and oligomers bridged by Pt(II) acetylides
(Chart 2).
Results and Discussion
Synthesis and Characterization. The starting materials,
Zn(II)[5,15-bis(mesityl)-10,20-bis(ethynyl)porphyrinate]
(L1) and Zn(II)[5,15-bis[3,4,5-tri(hexadecyloxy)phenyl]-
10,20-bis(ethynyl)porphyrinate] (L2), were prepared ac-
cording to the literature.8a,6j The reaction of L1 or L2 with
two equivalents of trans-chloro(ethynylbenzene)bis(tris-
n-butylphosphine)platinum(II) in the presence of CuI in
CH2Cl2 and iPr2NH (v/v, 1:1) gave the model compounds
M1 and M2 in 44-47% yield, while the same workup in
the reaction of L1 and L2 with trans-[Pt(P-n-Bu3)2Cl2]
gave plastic like materials for porphyrin oligomers P1 and
P2 in about 60% yield. M1 and M2 are characterized by
1H and 31P NMR, MALDI-TOF high resolution mass
spectrometry (HRMS), FT-IR, and thermal gravity ana-
lysis (TGA), each of which proves their molecular struc-
tures, shown in Scheme 2.

Article
Inorganic Chemistry, Vol. 49, No. 6, 2010 2617
Scheme 2. Synthetic Route for M1, M2, P1, and P2
Taking M1, for example, two doublets at 9.59 and 8.52 ppm
with the same J-coupling of 6.1 Hz in the proton NMR of
M1 are assigned to the protons at the β positions of the
pyrrole unit of the porphyrin macrocycle. These two doub-
lets confirm the symmetrical chemical structure. Two sing-
lets at 2.66 and 1.87 ppm are ascribed to the mesityl group
with an integration intensity ratio of 1:2. The combination
of a Pt(II) moiety with a porphyrin moiety is ascertained by
four multiplets in the region 2.34-0.89 ppm, which are
assigned to pendant n-butyl groups. In 31P NMR, the
chemical shift of phosphorus is shown at 5.87 ppm with
Figure 1. X-ray structure of M1. Hydrogen atoms are omitted for
clarity.
1
two satellite peaks giving a J-coupling JPt-P = 3100 Hz
solubility in chlorinated solvents, and therefore it was
washed with dichloromethane to remove the unreacted
starting materials. At last, a polydispersity of 1.41 was
obtained for P1. Despite its poor solubility, P1 can be
dissolved in 2-MeTHF in order to carry out all the photo-
physical measurements. The GPC results, using poly-
styrene as a standard and THF as the solvent, indicate that
the number-average molecular weights Mn for P1 and P2
are 7307 and 8349, respectively. Although it was reported
that the starting material L2 gave a Mn value of 3250
(higher than the theoretical value of 2016.51) caused by
overestimation of the molecular weight of rigid-rod poly-
mers with polystyrene as a standard,6j the Mn of L2 is
1917 similar with its theoretical value obtained from
GPC. From this analysis, the approximate number of
repeated units for P1 and P2 is 5.8 and 3.2, respectively.
The higher degree of polymerization for P1 versus that for
P2 may lay in the chemical structures since L2 is much
more bulky than L1, as it has several long alkyl chains at
its meso positions. This feature makes it harder for reac-
tants to interact. Attempts were made to obtain higher
degrees of polymerization for both oligomers using high-
er reaction temperatures but failed when the temperature
was higher than 65 °C. The peaks in 1H NMR spectra of
P1 and P2 are all broadened (except for those assigned to
which further proves the symmetrical conformation of this
compound. A peak at m/z 2057.799 shown in MALDI-
TOF-HRMS is the Mþ ion with a deviation of less than 1
ppm. The FT-IR spectrum shows no band at 3300 cm-1
(tC-H stretching vibration), while the band at 2080 cm-1
(CtC stretching vibration) further reveals the successful
coordination of the Pt(II) moiety onto the porphyrin-con-
taining ligands L1 and L2. Thermal gravity analysis shows
M1 and M2 are thermally stable with T10%decomp (tempe-
rature when 10% of the compound is decomposed) = 328
and 300 °C, respectively. Owing to the long hexadecyl
group, it is easier for M2 to lose methyl and other alkyl
groups. M1 and M2 are both air-stable and soluble in
common solvents such as chloroform, dichloromethane,
and tetrahydrofuran (THF), for example, but M2 is more
soluble than M1 due to its long side chains.
In order to reduce the polydispersity of the two porphy-
rin oligomers, different purification methods were at-
tempted. P2 is readily soluble in common solvents; hence
flash column chromatography on silica gel can be per-
formed. Better results are obtained when the solution of
P2 was dissolved in a minimum of dichloromethane
and methanol was added to induce a precipitation of P2
with a polydispersity of 1.43. However, P1 exhibits a low

2618 Inorganic Chemistry, Vol. 49, No. 6, 2010
Jiang et al.
Table 1. Photophysical Data for L1, L2, M1, M2, P1, and P2 in 2-MeTHF at 298 and 77 Ka
excitation (nm)
298 K 77 K
emission (nm)b
quantum yieldc
emission lifetimesd
298 K 77 K
λ
max (nm) (ε ꢀ 10-4M-1cm-1
432 (21.2), 442 (16.0), 576 (1.83), 432, 442 435, 447 626, 684 630, 687
)
298 K 77 K
298 K
0.14
77 K
0.14
L1
L2
2.37 ( 0.08 ns 3.13 ( 0.08 ns
1.93 ( 0.08 ns 0.19 ( 0.08 ns
622 (2.27)
434 (28.2), 444 (25.2), 574 (2.14), 434, 444 438, 452 629, 685 636, 701
622 (2.62)
0.068
0.012
0.011
0.0076
M1 314 (11.4), 456 (66.3), 606 (3.93), 456
658 (13.0)
337, 456 669, 742 437, 669, 0.082
745
0.46 ( 0.08 ns 32.6 ( 1.1 μs [Pt]e;
0.54 ( 0.08 ns
0.43 ( 0.08 ns 0.21 ( 0.08 ns
M2 316 (11.8), 456 (47.3), 606 (4.46), 456
658 (10.6)
459
671, 744 683, 759
0.0072
P1
P2
302 (7.72), 466 (23.5), 678 (9.98)
302 (9.26), 462 (25.4), 676 (7.60)
462
462
461
463
682, 754 684, 754
680, 750 685, 770
0.016
0.010
0.0034
0.0055
0.39 ( 0.08 ns 0.29 ( 0.08 ns
0.38 ( 0.08 ns
f
a All luminescence measurements at 298 K were performed under an inert atmosphere. The other measurements (absorption and luminescence) were
performed without degassing the solutions. b The fluorescence lifetimes were measured using λexc corresponding to the Soret band, and λemi corres-
ponding to the 0-0 of the fluorescence. c The uncertainties are on the order of (10%. d Lifetime decays are measured using λexc=437 nm; the decay traces
are placed in the SI; the uncertainty on the fluorescence lifetimes is based upon the variation of several measurements. e Phosphorescence arising from [Pt]
(i.e., (trans-Pt(P-n-Bu3)2(CtC-p-C6H4)2). f Too short to be accurately measured.
n-butyl groups in the range 0.8-2.3, which are sharp)
demonstrating the successful coupling between the por-
phyrin and Pt(II) moiety. This is further confirmed by
the FT-IR spectrum in which a band is observed at ca.
2080 cm-1 (ν(CtC)). The 31P NMR signals at 7.57 and
7.82 ppm are also traced for P1 and P2, respectively. We
find no signal attributable to the CC-H end group in the
1H spectra, meaning that the end groups in P1 and P2
must be the PtL2Cl residue. Thermal gravity analysis
shows the T10%decomp for P1 and P2 are 385 and 312 °C,
respectively, which coincides with the trend for M1 and M2.
A single crystal of M1 suitable for X-ray diffraction was
grown by slow evaporation of a mixture of a CH2Cl2/
Figure 2. Computed frontier MOs for an optimized geometry of L1 by
DFT, along with the computed pure electronic transitions and generated
absorption bands.
MeOH solution at room temperature. The crystal struc-
ture is shown in Figure 1, and the crystallographic data
are placed in Table S1 of the Supporting Information (SI).
The identity of M1 is of no doubt. The trans geometry of
the two Pt centers is demonstrated.
Table 2. TDDFT Parameters for the Four First Observable Electronic Transi-
tions for L1a
Spectroscopic Data, DFT and TDDFT Analyses. All
measurements are carried out in 2-MeTHF (Table 1). The
absorption spectra of the L1 and L2 (see Figure S5 in the
SI and refer to Table 1 for peak maxima; typical spectra
are also shown below for P1 and P2) exhibit split Soret
bands located at 432 and 442 nm and at 434 and 444 nm,
respectively. The splitting readily expected for porphyrins
of reduced symmetry is corroborated by DFT (B3LYP/
6-31G*) and TDDFT computations (B3LYP/6-31G*/
THF PCM model) as presented below. After geometry
optimization of L1, the computed frontier MOs (Figure 2)
unambiguously show the π nature of these MOs, hence
strongly indicating that the lowest energy transitions and
excited states are of the ππ* type. The computed lowest
energy transitions (TDDFT; Table 2) indeed show that the
four lowest energy transitions are mixtures of different
individual electronic transitions composed of these four
same MOs (green lines in Figure 2). The splitting is obvious
where a computed 10 nm (experimental 10 nm) is obtained
for the Soret band for L1. The relative intensity of the two
Soret bands is also felt in the oscillator strengths (Osc. Str.).
For the Q-band, two electronic transitions are computed
and separated by 7 nm. Experimentally, only a weak
shoulder is observed for L1 at 77 K at ∼615 nm, appearing
as a weak shoulder beside a stronger 0-0 peak at 623 nm.
A peak located at 576 nm is also apparent, but this feature
ν
λ
(nm) osc. str.
no. (cm-1
)
major contributions (%)
1
2
3
4
5
17 700 565 0.1402 H-1fLþ1 (31), HOMOfLUMO (66)
17 924 558 0.0018 H-1fLUMO (52), HOMOfLþ1 (51)
24 363 410 1.5022 H-1fLUMO (32), HOMOfLþ1 (34)
24 520 408 0.0017 H-6fLUMO (97)
25 112 398 1.3667 H-1fLþ1 (53), HOMOfLUMO (14)
a The S0 optimized geometry was first performed, followed by
TDDFT computations using 6-31G* basis sets for Zn, C, H, and N;
polarized basis sets for P; and SBKJC and VDZ with effective core
potentials for Pt and the THF PCM model.
may be of vibronic origin. A computed spectrum generated
by assigning a thickness of each individual transition resem-
bles the experimental (Figure S5, SI, and Table 1) well.
Because the calculated Q-band is 57 nm blue-shifted with
respect to the experimental one in L1, for example, both the
6-31G* and 3-21G* basis sets were used for Zn, C, H, and
N (the rest remains the same), and the THF PCM model
was used with all the TDDFT calculations to mimic the
2-MeTHF recorded spectra, for comparison purposes. The
results show that the calculated band maxima are more
blue-shifted for 3-21G* than for 6-31G* or for 6-31G*
coupled to the presence of THF (i.e., PCM THF model).
Only the most red-shifted data are placed in the text
(because it provides closer calculated data to the experimental

Article
Inorganic Chemistry, Vol. 49, No. 6, 2010 2619
Table 3. TDDFT Parameters for the Four First Observable Electronic Transitions for M1a
no.
ν (cm-1
)
λ (nm)
Osc. Str.
Major contributions (%)
1
2
3
4
5
6
7
8
9
17 262
17 443
17 948
18 170
23 712
23 808
24 125
24 202
24 461
579
573
557
550
422
420
415
413
409
0.0881
0.6136
0.0002
0
0.0175
0.0417
1.1066
0.3119
0.6202
H-2fLUMO (24), HOMOfLþ1 (65)
H-2fLþ1 (18), HOMOfLUMO (66)
H-1fLUMO (95)
H-1fLþ1 (95)
H-5fLUMO (21), H-4fLUMO (23), H-3fLUMO (42)
H-6fLUMO(16), H-5fLUMO(15), H-4fLUMO(47) H-3fLUMO (16)
H-6fLUMO (28), H-5fLUMO (12), H-2fLþ1 (30)
H-5fLUMO (43), H-3fLUMO (31)
H-4fLþ1 (18), H-2fLUMO (45), HOMOfLþ1 (10)
a The S0 optimized geometry was first performed, followed by TDDFT computations using 6-31G* basis sets for Zn, C, H, and N; polarized basis sets
for P; and SBKJC and VDZ with effective core potentials for Pt and the THF PCM model.
Figure 3. MO representations of the frontier MOs for M1 (from LUMOþ1 to HOMO-6). The geometry of M1 was optimized first using 6-31G* basis
sets for Zn, C, H, and N; polarized basis sets for P; and SBKJC and VDZ with effective core potentials for Pt.
values). The comparison of the calculated spectra and a
table for the TDDFT parameters for the first observable
electronic transitions for L1 using the 6-31G* basis set (no
THF PCM model added) are placed in the SI. Similar
computations and comparisons were made for M1 and
M2, described below, and led to the same observation
(SI). For M1 and M2, the discrepancy is 79 and 74 nm,
respectively, at best with 6-31G* with the PCM THF model.
Despite this difference, the conclusions are not affected (i.e.,
assignment of the nature of the excited states) since these are
well-known for porphyrin derivatives.
The chemical coupling of L1 and L2 onto two Pt
moieties results in the formation of compounds M1 and
M2. Both exhibit red-shifted Soret bands at 456 nm (see
Figure S6 in the SI) suggesting interactions between the
metal atom and the π-system via conjugation. For the
square-planar Pt acetylide complexes, it was reported that
there are strong interactions between metal dπ orbitals
and filled acetylide π orbitals, although no significant
metal-ligand back-bonding was found.13 Previous re-
search indicated that the electronic coupling through an
alkyne-Pt-alkyne bridge was only somewhat smaller
than through an alkyne-benzene-alkyne bridge, while
this case also appeared in this study.14 The coupling of L1
Figure 4. TDDFT computed electronic transitions and generated ab-
sorption bands for M1 using optimized geometries in the S0 state using 6-
31G*basis setsfor Zn, C, H, and N; polarizedbasis setsfor P;and SBKJC
and VDZ with effective core potentials for Pt and the THF PCM model.
and L2 with the PtL2 moiety leads to a material exhibiting
red shifts of both the Soret band and Q bands as well as an
enhancement of the intensity of Q-band. To corroborate
the experimental data, DFT and TDDFT calculations
were performed on M1 using the X-ray structure (Table 3),
whereas an optimized geometry for M2 was used where the
C16H33 chains were replaced by CH3 groups to save com-
putation time.
(13) (a) Schull, T. L.; Kushmerick, J. G.; Patterson, C. H.; George, C.;
Moore, M. H.; Pollack, S. K.; Shashidhar, R. J. Am. Chem. Soc. 2003, 125,
3202–3203. (b) Louwen, J. N.; Hengelmolen, R.; Grove, D. M.; Oksam, A.
Organometallics 1984, 3, 908–918.
The relevant frontier MOs for M1 and M2 are shown in
Figure 3 and in Figure S3 in the SI, respectively. Only the
description of M1 will be presented here. It is the same as
(14) Jones, S. C.; Coropceanu, V.; Barlow, S.; Kinnibrugh, T.; Timofeeva,
ꢀ
T.; Bredas, J.-L.; Marder, S. R. J. Am. Chem. Soc. 2004, 126, 11782–11783.

2620 Inorganic Chemistry, Vol. 49, No. 6, 2010
Jiang et al.
Figure 5. Absorption (blue), excitation (green), and emission spectra (red) of P1 (left) and P2 (right) in 2-MeTHF at 298 (top) and 77 K (bottom).
M2. Again, the HOMO, HOMO-1, LUMO, and
LUMOþ1 are all π systems bearing a strong resemblance
with that of L1. A minor contribution arising from the Pt
dxy orbital is computed for the LUMOþ1, hence corro-
borating evidence for Pt interactions. HOMO-3, -4, -5,
and -6 are interesting orbitals since they are specific to
the π systems in the -CtCPh arms present only in M1
and M2. This bears a consequence on the observation
of upper energy phosphorescence in M1. HOMO-1 is
the σ*(Zn-N) orbital accidentally degenerated with
HOMO-2.
The overall generated gas phase spectra for M1 and M2
(similar to the red line shown in Figure 2) resembles the
experimental ones (see Figure S2, Table S4 in the SI).
The major difference is that more bands in the Q and
Soret regions are computed (Figure 4). The key feature is
that the Soret region is composed of 4 calculated transi-
tions, three of them involving HOMO-3 and HOMO-6,
predicting the Soret band to exhibit a strong charge
transfer character from the CtCPtCtC unit to the MP
moiety along with the ππ* transition. This is indeed
consistent with the increase in absorptivity experimen-
tally observed for M1 and M2 (Table 1). However, the
major contribution of this transition is HOMO-6fLU-
MO and involved electronic density of the CtCPtCtC
π system (HOMO-6) oriented in a perpendicular manner
with respect to the π* porphyrin one (LUMO). So, it is
anticipated that this contribution (i.e., HOMO-6f
LUMO) does not play a major role in the overall intensity
of this Soret band.
that at 298 K, the luminescence spectra at 77 K are
sharper and slightly red-shifted. The fluorescence spectra
shift with the nature of the compounds, such as L1=L2<
M1 = M2 < P1 = P2, where the shift of the 0-0 peaks
may be up to 40-50 nm, indicating that conjugation is
preserved through the Pt atom by mixing of the frontier
MOs of Pt and ligands.15,16
During the course of this investigation, an upper-
energy phosphorescence was noted in the 400-550 nm
region for M1 at 77 K (Figure 6). This luminescence is
long-lived (∼32 μs; i.e., phosphorescence), and the spec-
trum bears a strong resemblance to that of trans-Pt(P-n-
Bu3)2(CtCC6H5)2, a unit (under the form of trans-Pt(P-
n-Bu3)2(CtC-p-C6H4)2=[Pt]) being part of oligomers or
polymers of the type ([Pt]-Ar)n where Ar = MP,12
C6X4N2 (X = Cl, OCH3, CH3).17 The excitation wave-
length necessary to observe this emission is about 350 nm,
and the Soret band is not visible in the absorption spectra,
confirming that this emission belongs to the [Pt] unit
(-PtL2CCPh) that is specific to M1 and M2. However,
this emission was not seen in M2. We have no explanation
for this absence of the upper energy luminescence in this
case.
In this work, it was not possible to investigate the
phosphorescence properties of the porphyrin MP units
in these materials. In our previous work,12b no phosphor-
escence of the MP chromophore was observed except
for rare cases such as polymer 9 (Chart 1). In that case,
polymer 9 exhibits a phosphorescence 0-0 peak at∼790 nm
The oligomers P1 and P2, again exhibiting an averaged
number of repetitive units of 5.8 and 3.2, respectively,
were investigated. In these cases, the Soret bands are even
more red-shifted down to 462 nm (Figure 5) in compa-
rison to those of M1 and M2 (and L1 and L2). The lowest
energy Q bands are even more red-shifted down to
678 and 676 nm, in comparison with 658 and 658 nm
for M1 and M2, respectively.
(15) Rogers, J. E.; Cooper, T. M.; Fleitz, P. A.; Glass, D. J.; McLean,
D. G. J. Phys. Chem. A 2002, 106, 10108–10115.
(16) (a) Wilson, J. S.; Dhoot, A. S.; Seeley, A. J. A. B.; Khan, M. S.;
€
Kohler, A.; Friend, R. H. Nature 2001, 413, 828–831. (b) Beljonne, D.;
€
Wittmann, H. F.; Kohler, A.; Graham, S.; Younus, M.; Lewis, J.; Raithby, P. R.;
ꢀ
Khan, M. S.; Friend, R. H.; Bredas, J.-L. J. Chem. Phys. 1996, 105, 3868–3877.
ꢀ
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(17) (a) Fortin, D.; Clement, S.; Gagnon, K.; Berube, J.-F.; Harvey, P. D.
Inorg. Chem. 2009, 48, 446–454. (b) Gagnon, K.; Aly, S. M.; Fortin, D.; Abd-El-
Aziz, A. S.; Harvey, P. D. J. Inorg. Organomet. Poly. Mat. 2009, 19, 28–34.
ꢀ
ꢀ
(c) Gagnon, K.; Aly, S. M.; Brisach-Wittmeyer, A.; Bellows, D.; Berube, J.-F.;
Caron, L.; Abd-El-Aziz, A. S.; Fortin, D.; Harvey, P. D. Organometallics 2008,
27, 2201–2214.
The fluorescence and excitation spectra for P1 and P2
at both 298 and 77 K are shown in Figure 5. Compared to

Article
Inorganic Chemistry, Vol. 49, No. 6, 2010 2621
Table 4. Calculated Position of the Phosphorescence 0-0 peaks for L1, M1,
and M2
ΔE(S0 - T1)/ λPhos
/
cpd.
basis sets
3-21G*
6-31G*
E(S0)/a.u.a E(T1)/a.u.a
a.u. nm
L1
L1
L1
-3598.8122 -3598.7580 0.0540
-3617.8760 -3617.8226 0.0534
841
853
875
863
857
6-31G*/THF -3617.8902 -3617.8381 0.0521
M1 6-31G*
M2 6-31G*
-7691.1800 -7691.1272 0.0528
-8139.9028 -8139.8497 0.0531
a From optimized geometries in the S0 and T1 states using 6-31G* or
3-21G* basis sets for Zn, C, H, and N; polarized basis sets for P; and
SBKJC and VDZ with effective core potentials for Pt.
Figure 6. Comparison of the emission (Em, λexc =337 nm) and excita-
tion (Ex, λemi = 437 nm) spectra of M1 and [Pt] (trans-Pt(P-n-Bu3)2-
(CtCC6H5)2).
of conjugated metal porphyrin-platinum(II) ethynyl units
were prepared and analyzed from a spectroscopic, DFT/
TDDFT, and photophysical point of view. Previously, etio-
porphyrins systems (where the β positions are occupied by
CH3 and CH2CH3 groups, and the meso positions remain
unsubstituted) were reported but were not investigated for
photophysical purposes. Upon conjugation through the
organometallic unit trans-Pt(PBu3)2, the absorption band
shifted down to 676-678 nm, which is a good wavelength
for photovoltaic applications.
(∼12 658 cm-1) and a fluorescence 0-0 signal at ∼605 nm
(∼16 529 cm-1), hence giving an S1-T1 gap of ∼3870 cm-1
.
By transferring this value to M1, M2, P1, and P2, one
would expect this 0-0 peak of phosphorescence in the
900 to 950 nm region. Our detector is sensitive down to
850 nm. Moreover, no long-lived signal was detected in
this 850 nm region.
We also attempted to calculate the position of the 0-0
peaks of the phosphorescence (λPhos) of the MP units
using DFT by estimating the S0-T1 gaps. Both geo-
metries in the S0 and T1 states for L1, M1, and M2 were
performed using the 3-21G*, 6-31G*, and 6-31G* sets
supplemented by a THF solvent field (6-31G*/THF), and
the S0, T1, and S0-T1 energies are thus calculated (Table 4).
The resulting calculated λPhos red shifts going from 3-21G*
to 6-31G* to 6-31G*/THF for L1 by a δ of 12 and 18 nm,
placing the 0-0 peak at 875 nm in the latter basis sets.
Similar conclusions are drawn for M1 and M2, which
indicate that the phosphorescence is placed at >850 nm.
If one also considers the discrepancy between the com-
putations and the experimental data discussed above for
the Q bands (computations are blue-shifted by about
60-80 nm), then the expected position of the 0-0 phos-
phorescence peak will most likely fall in the 930 nm
region. This is consistent with the experimental consid-
erations stated above.
Emisson Lifetimes and Quantum Yields. The fluore-
scence lifetimes (τF) and quantum yields (ΦF) are reported
in Table 1. The trend for both parameters approximatively
follows L1 ∼ L2 > M1 ∼ M2 ∼ P1 ∼ P2, which is a pre-
dictable consequence of the heavy atom effect induced by
the Pt atom (L1 and L2 versus M1, M2, P1, and P2) where a
decrease by about an order of magnitude is noted. Interest-
ingly, both τF and ΦF turned out to be only slightly affected
for the Pt-containing materials. A closer look at the data of
Table 1 indicates that both τF and ΦF are shorter for L2,
M2, and P2 in comparison with L1, M1, and P1, respec-
tively, most likely reflecting a loose bolt effect induced by the
addition of flexible side chains (OC16H33). We also find that
both τF and ΦF follow an approximate trend of ligand <
model < oligomer. This observation probably reflects the
same effect mentioned above: as the number of flexible
chains increases, both τF and ΦF decrease. The unexpectedly
large decrease in τF (∼5 fold) and ΦF (∼10 fold) for M2 at
77 K from 298 K is still unexplained.
Two points were raised in this work. The first one is
that there is a major change in photophysical properties
(τF and ΦF) when the size of the conjugated oligomers and
polymers increases. To answer this question, molecules of
nanometer dimensions must be examined, such as those
presented here (a repetitive unit is on the order of 1.61 nm,
the distance between two Pt atoms in M1). So M1 is of
2 nm dimensions and P1 is about 7.2 nm. The answer to
this question is that only slightly perturbed parameters
are observed where a small decrease in τF and ΦF is noted.
This means that for photovoltaic applications, as the
oligomer or the polymer gets longer, nonradiative pro-
cesses get only slightly more efficient, and so the antenna
effect (more specifically energy delocalizations and en-
ergy transfers across the materials) is not drastically
reduced. On the other hand, as the dimension increases,
the extent of energy migration should increase without a
major loss of excitation through nonradiative processes
such as internal conversion and intersystem crossing.
The second point is, how can we find the difference or
confidently assign a decrease in photophysical para-
meters to either internal conversion (from the singlet
and triplet) vs energy transfer? The conjugated molecules
and oligomers investigated in this work were selected
purposely as they are approximately of the same dimen-
sion as the model compound 8 and oligomers 10 (Chart 1)
and they are fully conjugated. The full conjugation makes
each oligomer practically a distinct molecule with no
possibility of intramolecular energy transfer. The oligo-
mer 10, which was investigated under the form of n=3, 6,
and 9, exhibits two distinct chromophores (trans-Pt(P-n-
Bu3)2(CtC-p-C6H4)2 as [Pt], and MP) readily depicted
from their respective luminescences. The rates for T1
energy transfer, kET, from [Pt] (trans-Pt(P-n-Bu3)2(CtC-p-
C6H4)2) as the energy donor to MP as the acceptor, and
measured from the decrease in phosphorescence lifetimes,
τP, of the [Pt] (in comparison with trans-Pt(P-n-Bu3)2-
(CtCC6H5)2 a model compound) varied from on the
order of 103 to 104 to 105 s-1 for n = 3, 6, and 9, respec-
tively. The model compound in this case (compound 8 in
Comparison of the Photophysical Properties with Other
Pt-Acetylide/Porphyrin Oligomers. New oligomeric species

2622 Inorganic Chemistry, Vol. 49, No. 6, 2010
Jiang et al.
Chart 1 for example) exhibits a rate slightly smaller than that
for polymer 10 (n=3) perfectly consistent with the change in
oligomer dimension. The interpretation of this photophysi-
cal event is the presence of an exciton process that delocalizes
the excitation energy over the oligomer despite the lesser
conjugated (A-B)n nature of the material. The T1 kET gets
faster as the extent of delocalization becomes longer. In this
work, no energy transfer is possible, and the observed effect
is just a modest decrease of the emission lifetimes. This is
particularly apparent when comparing M1 (1 unit) with P1
(∼6 units) at 298 K. One would expect 2 orders of magnitude
of variation based on the trend indicated for monomer 8 and
polymer 10 (n=6).
methane and purified by column chromatography on silica gel
using dichlormethane/hexane (1:1, v/v) as an eluent. M1 was
obtained in 44% yield. 1H NMR (CDCl3, 400 MHz): δ 0.89 (m,
36 H), 1.39-1.46 (m, 24 H), 1.75-1.80 (m, 24 H), 1.87 (s, 12 H),
2.26-2.34 (m, 24 H), 2.66 (s, 6 H), 7.24-7.29 (m, 10 H), 7.38 (d,
4H, J = 10.3 Hz), 8.52 (d, 4H, J = 6.1 Hz), 9.59 (d, 4H, J = 6.1
Hz). 31P NMR (CDCl3, 160 MHz): δ 5.87 (1JPt-P = 3100 Hz).
MOLDI-TOF MS: 2057.799 (Mþ). Elem anal. calcd (%) for
C106H148N4P4Pt2Zn: C 61.87, H 7.25, N 2.72. Found: C 61.47, H
7.33, N 2.55. IR (v/cm-1): 2080. TGA: T10%decomp =328 °C.
Zn(II){5,15-bis[3,4,5-tri(hexadecyloxy)phenyl]-10,20-bis[2-(ethy-
nylbenzene)bis(tri-n-butyl-phosphine)platinum(II)ethynyl]por-
phyrin} (M2). L2 (200 mg, 0.099 mmol) was reacted with trans-
chloro(ethynylbenzene)bis(tri-n-butyl-phosphine)platinum(II)
(148 mg, 0.200 mmol) in cosolvent iPr2NH-CH2Cl2 (100 mL,
1:1, v/v) in the presence of CuI (4 mg, 0.020 mmol) for 12 h at
room temperature under argon. The solvents were removed with
an evaporator under low pressure. The solid was dissolved in
minimum dichloromethane and purified by column chromato-
graphy on silica gel using dichlormethane/hexane (1:1, v/v) as a
Conclusion
The conjugated oligomers P1 and P2 exhibit intense and
red-shifted Soret and Q-bands. In a situation of a photo-
induced electron transfer from the fully conjugated polymer
to an added electron acceptor (such as C60 for example), the
polymer will become cationic, a positive charge that would be
delocalized along the backbone. This behavior combined
with the strong absorptivity of two bands placed in the visible
region of the spectrum (Soret and Q-band) would make the
polymers potential materials for photovoltaic applications.
In comparison with L1 and L2, there is no drastic decrease in
photophysical parameters (factor going from 2 to 3 from
Table 1), meaning that there is a minimal decrease in the
potential efficiency in the antenna effect (i.e., capturing and
migrating the excitation energy across the material) as the
rate for nonradiative deactivation is not expected to increase
drastically. These oligomers should indeed be examined for
photovoltaic performances in order to confirm this in the
near future. Moreover, these conjugated oligomers were
selected because they acted as distinct molecules where no
energy transfer could occur. The conclusion drawn from the
photophysical analysis for the 6 compounds investigated is
that one can now separate the effect of the oligomer dimen-
sion on the photophysical parameters from the stronger
influence of the exciton process and energy transfers on them.
1
eluent. M2 was obtained in 47% yield. H NMR (CDCl3, 400
MHz): δ 0.83-0.93 (m, 54 H), 1.21-1.27 (m, 168 H), 1.37-1.49
(m, 24 H), 1.80-1.88 (m, 24H), 2.28 (m, 24 H), 4.09 (t, 8H, J=
8.5 Hz), 4.30 (t, 4H, J =8.5 Hz), 7.10-7.30 (m, 10 H), 7.38 (d,
4H, J=10.3 Hz), 8.80 (d, 4H, J=6.0 Hz), 9.64 (d, 4H, J=6.0
Hz). 31P NMR (CDCl3, 160 MHz): δ 5.95 (1JPt-P = 3100 Hz).
MOLDI-TOF MS: 3414.219 (Mþ). Elem anal. calcd (%) for
C196H328N4P4Pt2Zn: C 68.91, H 9.68, N 1.64. Found: C 68.45, H
10.00, N 1.57. IR (v/cm-1): 2081. TGA: T10%decomp =300 °C.
Poly{Zn(II)[5,15-bis(mesityl)-10-ethynyl-20-(2-trans-bis(tri-
n-butylphosphine)platinum(II)-ethynyl)]}porphyrin (P1). L1
(50 mg, 0.076 mmol) was reacted with trans-[Pt(P-n-Bu3)2Cl2]
(51 mg, 0.076 mmol) in cosolvent iPr2NH-CH2Cl2 (80 mL, 1:1,
v/v) in the presence of CuI (2 mg, 0.010 mmol) for 12 h at 65 °C
under argon. All the volatile compounds were removed under
reduced pressure. The residue was redissolved in CH2Cl2 and
filtered through a short silica column using dichloromethane as
an eluent to give a green solution of the polymeric material.
After the removal of solvent by a rotary evaporator, the product
was then reprecipitated twice from a CH2Cl2/MeOH mixture
followed by washing with MeOH to afford a green solid in 60%
yield. 1H NMR (CDCl3, 400 MHz): δ 0.8-1.0 (m), 1.1-1.5 (m),
1.6-1.7 (broad peak (br)), 1.8-1.9 (m), 2.1-2.3 (br), 2.4 (br),
2.6-2.7 (m), 7.2-7.4 (m), 8.5-8.7 (br), 9.6-9.8 (br). 31P NMR
(CDCl3, 160 MHz): δ 7.57 ppm. IR (v/cm-1): 2081. GPC (THF):
Mw= 10487, Mn= 7307, PD=1.43. TGA: T10%decomp=385 °C.
Poly{Zn(II)[5,15-bis(3,4,5-tri(hexadecyloxy)phenyl)-10-ethynyl-
20-(2-trans-bis(tri-n-butyl-phosphine)platinum(II)ethynyl)por-
phyrin]} (P2). L2 (70 mg, 0.035 mmol) was reacted with
trans-[Pt(P-n-Bu3)2Cl2] (24 mg, 0.035 mmol) in cosolvent
iPr2NH-CH2Cl2 (80 mL, 1:1, v/v) in the presence of CuI (2 mg,
0.010 mmol) for 12 h at 65 °C under argon. The resulting
solution was diluted by 100 mL of CH2Cl2 and washed with
water three times. The organic layer was collected, and the
volatile compounds were removed under reduced pressure.
The residue was washed with CH2Cl2 thoroughly to remove
the starting materials. This resulted in a dark green solid in 62%
yield. 1H NMR (CDCl3, 400 MHz): δ 0.8-1.0 (m), 1.1-1.5 (m),
1.7 (br), 1.8-2.0 (br), 2.4 (br), 4.1 (br), 4.3 (br), 7.4-7.5 (br), 8.9
(br), 9.8 (br). 31P NMR (CDCl3, 160 MHz): δ 7.82. IR (v/cm-1):
2081. GPC (THF): Mw= 11836, Mn= 8349, PD=1.41. TGA:
T10%decomp =312 °C.
Experimental Section
Materials. All reactions were carried out under an argon
atmosphere by using standard Schlenk techniques. Solvents
were dried and distilled from appropriate drying agents under
an inert atmosphere prior to use. Glassware was oven-dried at
about 120 °C. All reagents and chemicals, unless otherwise
stated, were purchased from commercial sources and used
without further purification. Zn(II)(5,15-bis(mesityl)-10,20-bis-
(ethynyl)porphyrinate) (L1),8a Zn(II)(5,15-bis[3,4,5-tri(hexade-
cyloxy)phenyl]-10,20-bis(ethynyl)porphyrinate) (L2),6j trans-
chloro(ethynylbenzene)bis(trin-butyl-phosphine)platinum(II),18
and trans-[Pt(P-n-Bu3)2Cl2]19 were prepared according to the
literature methods.
Zn(II){5,15-bis(mesityl)-10,20-bis[2-(ethynylbenzene)bis(tri-
n-butylphosphine)platinum(II)-ethynyl]porphyrin} (M1) L1
(50 mg, 0.076 mmol) was reacted with trans-chloro-(ethynyl-
benzene)bis(trin-butyl-phosphine)platinum(II) (113 mg, 0.153
mmol) in cosolvent iPr2NH-CH2Cl2 (80 mL, 1:1, v/v) in the
presence of CuI (2 mg, 0.010 mmol) for 12 h at room temperature
under argon. The solvents were removedwithanevaporator under
low pressure. The solid was dissolved in minimum dichloro-
Instrumentation. Infrared spectra were recorded as powder or
THF solutions using a Perkin-Elmer Paragon 1000 PC or
Nicolet Magna 550 Series II FTIR spectrometer, using CaF2
cells with a 0.5 mm path length. NMR spectra were measured in
appropriate deuterated solvents on a JEOL EX270 or a Varian
Inova 400 MHz FT-NMR spectrometer, with 1H NMR chemi-
cal shifts quoted relative to SiMe4, and 31P chemical shifts
(18) Miki, S.; Ohno, T.; Iwasaki, H.; Yoshida, Z. J. Phys. Org. Chem.
1988, 1, 333.
(19) Kauffman, B.; Teter, L. A.; Huheey, J. E. Inorg. Synth. 1963, 7, 245.

Article
Inorganic Chemistry, Vol. 49, No. 6, 2010 2623
ꢀ
with a Mammouth MP supercomputer supported by le Reseau
relative to an 85% H3PO4 external standard. Fast-atom bom-
bardment (FAB) mass spectra were recorded on a Finnigan
MAT SSQ710 mass spectrometer in m-nitrobenzyl alcohol
matrices. The molecular weights of the polymers were deter-
mined by GPC (HP 1050 series HPLC with visible wavelength
and fluorescent detectors) using polystyrene standards and THF
as an eluent, and the thermal analyses were performed with the
Perkin-Elmer TGA6 thermal analyzer. The UV/vis spectra
were recorded on a Hewlett-Packard diode array model 8452
A at Sherbrooke. The emission and excitation spectra were
obtained by using a double monochromator Fluorolog 2 instru-
ment from Spex. Fluorescence and phosphorescence lifetimes
were measured on a Timemaster Model TM-3/2003 apparatus
from PTI. The source was a nitrogen laser with a high-resolution
dye laser (fwhm ≈ 1.5 ns), and the fluorescence lifetimes were
obtained from high-quality decays and deconvolution or dis-
tribution lifetime analysis. The uncertainties were about (40 ps
based on multiple measurements.
25-28
ꢀ ꢀ
Quebecois de Calculs de Haute Performances. The DFT
and TDDFT29-31 were calculated using the B3LYP32-34 meth-
od. 6-31G* or 3-21G*35-40 basis sets were used for Zn, C, H, and
N; polarized basis sets for P;41,42 and SBKJC and VDZ with
effective core potentials43-45 were used for platinum. The
calculated absorption spectra and related MO contributions
were obtained from the TD-DFT/Singlets output file and
gausssum2.1.46 THF PCM47 model was used with all the
TDDFT calculations to mimic the 2-MeTHF recorded spectra.
Acknowledgment. This research was supported by the Natu-
ral Sciences and Engineering Research Council of Canada
ꢀ ꢀ
(NSERC), le Fonds Quebecois de la Recherche sur la Nature
ꢀ
et les Technologies (FQRNT), and the Centre d’Etudes
ꢀ
des Materiaux Optiques et Photoniques de l’Universite de
Sherbrooke.
ꢀ
Supporting Information Available: Crystal data and structure
refinement for M1; comparison of the calculated spectra for L1
as a function of the basis set and the presence of THF; TDDFT
parameters for the first observable electronic transitions for M2;
comparison of the calculated spectra for M1 and M2; TDDFT
parameters for the four first observable electronic transitions for
M1; TDDFT parameters for the four first observable electronic
transitions for M2; decay traces for all compounds and poly-
mers investigated in this work; absorption, excitation and
emission spectra of L1 and L2 in 2-MeTHF at 298 and 77 K;
absorption, excitation, and emission spectra of M1 and M2 in
2-MeTHF at 298 and 77 K; intergrated fluorescence intensity as
a function of the absorbance of the Soret band where all
excitations takes place; Cartesian coordinates of the optimized
geometry for L1, M1, and M2; X-ray crystallographic files in
CIF format. This material is available free of charge via the
Internet at http://pubs.acs.org.
Quantum Yield Measurements. For room-temperature mea-
surements, all samples were prepared under an inert atmosphere
(in a glovebox, PO2 < 20 ppm) by dissolution of the different
compounds in 2-MeTHF using 1 mL quartz cells with septum
(298 K) or quartz NMR tubes in liquid nitrogen for 77 K
measurements. Three different measurements (i.e., different
solutions) were performed for each set of photophysical data
(quantum yields, ΦF). The sample concentrations were chosen
to correspond to an absorbance of 0.05 at the excitation
wavelength. Each absorbance value was measured five times
for better accuracy in the measurements of emission quantum
yield (ΦF). The ΦF was referenced to tretraphenylporphyrin,
H2TPP (ΦF =0.11 in 2-MeTHF at 77 K).20 The concentration
used for the photophysical examination is around 0.1ꢀ10-6 to
1 ꢀ 10-6 M. The quantum efficiency was also checked by mea-
suring absorbance and integrated fluorescence at various con-
centrations. The results of such measurements are placed in
Figure S7 in the SI where the gradient of the curves becomes
proportional to the relative quantum yield of the different
samples.
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X-Ray Crystallography. The crystals were grown by slow
evaporation of a mixture of a CH2Cl2/MeOH solution at room
temperature. One single crystal of 0.10 ꢀ 0.30 ꢀ 0.80 mm3 was
mounted using a glass fiber at 198(2) K on the goniometer. Data
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ꢀ
ometer at the Universite de Sherbrooke using ω scans. The
DIFRAC21 program was used for centering, indexing, and data
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