Unusual frequency dispersion effects of the nonlinear optical response in highly conjugated (polypyridyl)metal-(porphinato)zinc(II) chromophores

Article abstract of DOI:10.1021/ja020651q

The syntheses and electrooptic properties of a new family of nonlinear optical chromophores are reported. These species feature an ethyne-elaborated, highly polarizable porphyrinic component and metal polypyridyl complexes that serve as integral donor and acceptor elements. Examples of this structural motif include ruthenium(II) [5-(4′-ethynyl-(2,2′;6′, 2″-terpyridinyl))-10,20-bis(2′,6′-bis(3, 3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)- (2,2′;6′,2″-terpyridine)²⁺ bis-hexafluorophosphate (Ru-PZn); osmium(II) [5-(4′-ethynyl-(2,2′;6′, 2″-terpyridinyl))-10,20-bis(2′,6′-bis(3, 3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)-(2, 2′;6′,2″-terpyridine)²⁺ bis-hexafluorophosphate (Os-PZn); ruthenium(II) [5-(4′-ethynyl-(2,2′;6′, 2″-terpyridinyl))-15-(4′-nitrophenyl)ethynyl-10, 20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy) phenyl)porphinato]zinc(II)-(2,2′;6′, 2″-terpyridine)²⁺ bis-hexafluorophosphate (Ru-PZn-A); osmium(II) [5-(4′-ethynyl- (2,2′;6′,2″-terpyridinyl))-15- (4′-nitrophenyl)ethynyl-10,20-bis(2′, 6′-bis(3,3-dimethyl-1-butyloxy)phenyl) porphinato]zinc(II)-(2,2′;6′,2″-terpyridine)²⁺ bis-hexafluorophosphate (Os-PZn-A); and ruthenium(II) [5-(4′-ethynyl- (2,2′;6′,2″-terpyridinyl))osmium(II) -15-(4′-ethynyl-(2,2′;6′,2″-terpyridinyl))-10,20-bis (2′,6′-bis(3,3-dimethyl-1-butyloxy)phenyl) porphinato]zinc(Il)-bis(2,2′;6′, 2″-terpyridine)⁴⁺ tetrakis-hexafluorophosphate (Ru-PZn-Os). The frequency dependence of the dynamic hyperpolarizability of these compounds was determined from hyperRayleigh light scattering (HRS) measurements carried out at fundamental incident irradiation wavelengths (λ_inc) of 800, 1064, and 1300 nm. These data show that (i) coupled oscillator photophysics and metal-mediated cross-coupling can be exploited to elaborate high β₀ supermolecules that exhibit significant excited-state electronic communication between their respective pigment building blocks; (ii) high-stability metal polypyridyl compounds constitute an attractive alternative to electron releasing dialkyl- and diarylamino groups, the most commonly used donor moieties in a wide range of established nonlinear optical dyes; (iii) this design strategy enables ready elaboration of chromophores having extraordinarily large dynamic hyperpolarizabilities (β_λ values) at telecommunication relevant wavelengths; and (iv) porphyrin B- and Q-state-derived static hyperpolarizabilities (β₀ values) can be designed to have the same or opposite sign in these species, thus providing a new means to regulate the magnitude of λ_inc-specific dynamic hyperpolarizabilities.

Full text of DOI:10.1021/ja020651q

Published on Web 10/25/2002
Unusual Frequency Dispersion Effects of the Nonlinear
Optical Response in Highly Conjugated
(Polypyridyl)metal-(Porphinato)zinc(II) Chromophores
H. Tetsuo Uyeda,† Yuxia Zhao,‡ Kurt Wostyn,‡ Inge Asselberghs,‡ Koen Clays,*,‡
Andre´ Persoons,*,‡ and Michael J. Therien*,†
Contribution from the Department of Chemistry, UniVersity of PennsylVania,
Philadelphia, PennsylVania 19104-6323 and Center for Research on Molecular
Electronics and Photonics, UniVersity of LeuVen, B-3001 LeuVen, Belgium
Received May 6, 2002
Abstract: The syntheses and electrooptic properties of a new family of nonlinear optical chromophores
are reported. These species feature an ethyne-elaborated, highly polarizable porphyrinic component and
metal polypyridyl complexes that serve as integral donor and acceptor elements. Examples of this
structural motif include ruthenium(II) [5-(4′-ethynyl-(2,2′;6′,2′′-terpyridinyl))-10,20-bis(2′,6′-bis(3,3-di-
methyl-1-butyloxy)phenyl)porphinato]zinc(II)-(2,2′;6′,2′′-terpyridine)2+ bis-hexafluorophosphate (Ru-PZn);
osmium(II) [5-(4′-ethynyl-(2,2′;6′,2′′-terpyridinyl))-10,20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)phenyl)por-
phinato]zinc(II)-(2,2′;6′,2′′-terpyridine)2+ bis-hexafluorophosphate (Os-PZn); ruthenium(II) [5-(4′-ethynyl-
(2,2′;6′,2′′-terpyridinyl))-15-(4′-nitrophenyl)ethynyl-10,20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)phen-
yl)porphinato]zinc(II)-(2,2′;6′,2′′-terpyridine)2+ bis-hexafluorophosphate (Ru-PZn-A); osmium(II) [5-(4′-ethynyl-
(2,2′;6′,2′′-terpyridinyl))-15-(4′-nitrophenyl)ethynyl-10,20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)-
phenyl)porphinato]zinc(II)-(2,2′;6′,2′′-terpyridine)2+ bis-hexafluorophosphate (Os-PZn-A); and ruthenium(II)
[5-(4′-ethynyl-(2,2′;6′,2′′-terpyridinyl))osmium(II)-15-(4′-ethynyl-(2,2′;6′,2′′-terpyridinyl))-10,20-bis
(2′,6′-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)-bis(2,2′;6′,2′′-terpyridine)4+ tetrakis-hexafluo-
rophosphate (Ru-PZn-Os). The frequency dependence of the dynamic hyperpolarizability of these
compounds was determined from hyperRayleigh light scattering (HRS) measurements carried out at
fundamental incident irradiation wavelengths (λinc) of 800, 1064, and 1300 nm. These data show that (i)
coupled oscillator photophysics and metal-mediated cross-coupling can be exploited to elaborate high â0
supermolecules that exhibit significant excited-state electronic communication between their respective
pigment building blocks; (ii) high-stability metal polypyridyl compounds constitute an attractive alternative
to electron releasing dialkyl- and diarylamino groups, the most commonly used donor moieties in a wide
range of established nonlinear optical dyes; (iii) this design strategy enables ready elaboration of
chromophores having extraordinarily large dynamic hyperpolarizabilities (âλ values) at telecommunication
relevant wavelengths; and (iv) porphyrin B- and Q-state-derived static hyperpolarizabilities (â0 values) can
be designed to have the same or opposite sign in these species, thus providing a new means to regulate
the magnitude of λinc-specific dynamic hyperpolarizabilities.
Introduction
We demonstrate as an alternative strategy that appropriate
coupling of multiple charge transfer (CT) oscillators can give
rise to supermolecular systems which feature substantial dy-
Conventional chromophores for nonlinear optical (NLO)
applications are based typically on design concepts that involve
optimizing the electron releasing and electron withdrawing
components, or conjugation length, of a particular dye platform.1-4
namic hyperpolarizabilities (âλ values).
We report herein archetypal examples of such supermolecular
NLO chromophores, describing their synthesis, electronic
spectroscopy, potentiometric properties, and frequency-depend-
ent hyperpolarizabilities determined via hyperRayleigh light
scattering (HRS) measurements. These systems exploit an
ethyne-elaborated, highly polarizable porphyrinic component and
metal polypyridyl complexes that serve as integral donor (D)
and acceptor (A) elements; examples of such structures are
shown in Chart 1.
* To whom correspondence may be sent. E-mail: koen.clays@fys.
kuleuven.ac.be; andre.persoons@fys.kuleuven.ac.be; therien@a.chem.
upenn.edu.
† University of Pennsylvania.
‡ University of Leuven.
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The rigid, cyllindrically π-symmetric connectivity between
the [porphinato]zinc(II) (PZn) and metal(II)polypyridyl units in
9
13806
J. AM. CHEM. SOC. 2002, 124, 13806-13813
10.1021/ja020651q CCC: $22.00 © 2002 American Chemical Society

(Polypyridyl)metal−(Porphinato)zinc(II) Chromophores
Chart 1. Structure of Investigated Compounds
A R T I C L E S
for 1H NMR spectra are relative to the solvent residual protium (CDCl3,
δ ) 7.24 ppm; acetonitrile-d3, δ ) 1.93 ppm; pyridine-d5, δ ) 8.74
ppm). All J values are reported in Hertz. The number of attached protons
is found in parentheses, following the chemical shift value. Chromato-
graphic purification (silica gel 60, 230-400 mesh, EM Scientific) of
all newly synthesized compounds was accomplished on the benchtop.
High-resolution mass spectroscopic analyses were performed at the
University of Pennsylvania Mass Spectrometry Center. Standard
abbreviations for metal polypyridyl compounds and terpyridyls are used
throughout the Experimental Section.
Instrumentation. Electronic spectra were recorded on an OLIS UV-
vis/near-IR spectrophotometry system that is based on the optics of a
Cary 14 spectrophotometer. Emission spectra were recorded on a SPEX
Fluorolog luminescence spectrophotometer that utilized a T-channel
configuration with a red sensitive R2658 Hamamatsu PMT and liquid
nitrogen cooled InGaAs detector; these spectra were corrected using
the spectral output of a calibrated light source supplied by the National
Bureau of Standards. Cyclic voltammetric measurements were carried
out on an EG&G Princeton Applied Research model 273A potentiostat/
galvanostat. The electrochemical cell used for these experiments utilized
a platinum disk working electrode, a platinum wire counter electrode,
and a saturated calomel reference electrode (SCE). The reference
electrode was separated from the bulk solution by a junction bridge
filled with the corresponding solvent/supporting electrolyte solution.
The ferrocene/ferrocenium redox couple was utilized as an internal
potentiometric standard.
HyperRayleigh Light Scattering (HRS) Measurements. The
experimental setup for the nanosecond hyperRayleigh scattering experi-
ments at 1064 nm has been described in detail.21 Femtosecond HRS
experiments were performed at 800 nm22 and at 1300 nm.23 The chro-
mophores were dissolved in dichloromethane and passed through 0.2-
µm filters. Crystalviolet chloride (CV, 338 × 10-30 esu in CH3OH),
p-nitroaniline (PNA, 21.6 × 10-30 esu in CH2Cl2), and disperse red 1
(DR1, 54 × 10-30 esu in CHCl3) were utilized as reference chro-
mophores at 800, 1064, and 1300 nm, respectively. For these external
references in different solvents, standard local field correction factors
were applied [((n2D + 2)/3)3, where n is the refractive index of the
solvent at the sodium D line]. Note that these experiments were
performed at low chromophore concentrations [< 3 × 10-6 M-1 (1064
these systems aligns the CT transition dipoles of the chro-
mophoric components in a head-to-tail arrangement and enforces
exceptional excited-state interpigment electronic communication
within the supermolecule. The electrooptic properties of these
assemblies not only underscore the prominent role that coupled
oscillator photophysics can play in the elaboration of chromo-
phores with exceptional dynamic hyperpolarizabilities. They
demonstrate also that such photophysics provides a powerful
means to engineer frequency dispersion effects in the chromo-
phoric NLO response that have, heretofore, been without
precedent.
Experimental Section
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2002, 33, 55-61.
Materials. All manipulations were carried out under nitrogen
previously passed through an O2 scrubbing tower (Schweizerhall R3-
11 catalyst) and a drying tower (Linde 3-Å molecular sieves) unless
otherwise stated. Air-sensitive solids were handled in a Braun 150-M
glovebox. Standard Schlenk techniques were employed to manipulate
air-sensitive solutions. All solvents utilized in this work were obtained
from Fisher Scientific (HPLC Grade). Tetrahydrofuran (THF) was
distilled from Na/benzophenone under N2. Diethylamine and triethyl-
amine were dried over KOH pellets and distilled under vacuum. All
NMR solvents were used as received. Reagents 3,3-dimethyl-1-butanol,
resorcinol, diethylazodicarboxylate (DEAD), triphenylphosphine (PPh3),
n-butyllithium, boron trifluoride etherate (BF3‚OEt2), tetramethyleth-
ylenediamine (TMEDA), 1,2-dichloro-4,5-dicyanobenzoquinone (DDQ),
2,6-bis-pyridyl-4-(1H)-pyridone, phosphorus pentabromide (PBr5),
phosphorus oxybromide (POBr3), potassium carbonate (K2CO3), potas-
sium nitrate (KNO3), potassium fluoride, N-ethylmorpholine, am-
monium hexafluorophosphate (NH4PF6), sodium borohydride, trifluo-
roacetic acid, N-bromosuccinimide (NBS), zinc(II) acetate, TBAF (1
M in THF), methyllithium (lithium bromide complex, 1.5 M, hexanes),
2,2′;6′,2′′-terpyridine (tpy), RuCl3, Na2OsCl6, trimethylsilylacetylene,
triisopropylsilylacetylene, ZnCl2 Pd2dba3, AsPh3, Pd(PPh3)4, triisopro-
pylamine, and copper(I) iodide were used as received (Aldrich or
Strem). Compounds 2,2′-dipyrrylmethane,5 trimethylsilylethynyl zinc
chloride,6 4′-bromo-(2,2′;6′,2′′-terpyridine)7-10 (Br-tpy), Ru(tpy)Cl3,11-15
and Os(tpy)Cl316-20 were prepared by literature methods. Chemical shifts
(6) Lin, V. S. Y.; DiMagno, S. G.; Therien, M. J. Science (Washington D. C.)
1994, 264, 1105-1111.
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1500.
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9
J. AM. CHEM. SOC. VOL. 124, NO. 46, 2002 13807

A R T I C L E S
Uyeda et al.
nm) and < 3 × 10-5 M-1 (800 and 1300 nm)]; the linearity of the
HRS signal as a function of chromophore concentration confirmed that
no significant self-absorption of the SHG signal occurred in these
experiments.
Ruthenium(II) [5-(4′-Ethynyl-(2,2′;6′,2′′-terpyridinyl))-15-(4′-ni
trophenyl)ethynyl-10,20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)-
phenyl)porphinato]zinc(II)-(2,2′;6′,2′′-terpyridine)2+ Bis-hexafluo-
rophosphate ([Ru-PZn-A], 3). [5-[(4′-Nitrophenyl)ethynyl]-15-ethy-
nyl-10,20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc-
(II) (160 mg, 0.15 mmol), Ru(tpy)2Br (265 mg, 0.28 mmol), diisopro-
pylamine (5 mL), THF (20 mL), and acetonitrile (30 mL) were brought
together in an oven-dried 100-mL Schlenk tube. The solution was
degassed via three freeze-pump-thaw cycles, following which
Pd(PPh3)4 (50 mg, 0.04 mmol) and CuI (25 mg, 0.13 mmol) were added.
The reaction was stirred under N2 at 70 °C for 24 h, the solution was
cooled to room temperature, and the solvent was evaporated. Compound
3 was purified by column chromatography on silica using 80:17:3
acetonitrile/water/saturated KNO3 as the eluant. The product eluted as
a brownish-green band; the volume of the product fraction was reduced
to 50 mL, and ammonium hexafluorophosphate (1 g) in 10 mL of water
was added, producing a brown precipitate. The product was filtered,
washed successively with water and ether, and dried to give 230 mg
of compound 3 as the hexafluorophosphate salt (79% yield, based on
265 mg of the [5-[(4′-nitrophenyl)ethynyl]-15-ethynyl-10,20-bis(2′,6′-
bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II) starting mate-
rial). 1H NMR (250 MHz, CD3CN): 9.92 (d, 2H, J ) 4.5 Hz), 9.37 (s,
2H), 9.30 (d, 2H, J ) 4.4 Hz), 8.94 (d, 2H, J ) 4.4 Hz), 8.80 (m, 6H),
8.52 (d, 4H, J ) 8.1 Hz), 8.45 (t, 1H, J ) 8.0 Hz), 8.04 (t, 2H, J ) 7.7
Hz), 7.95 (t, 2H, J ) 7.8 Hz), 7.86 (t, 2H, J ) 8.5 Hz), 7.57 (d, 2H,
J ) 5.5 Hz), 7.42 (d, 2H, J ) 5.5 Hz), 7.24 (m, 8H), 6.91 (d, 2H, J )
8.5 Hz), 4.07 (t, 8H, J ) 7.2 Hz), 0.96 (t, 8H, J ) 7.2 Hz), 0.30 (s,
36H). MS (MALDI-TOF) m/z: 1661 (calcd for C96H91N11O6RuZn (M
- 4PF6)+ 1661) m/z: 1807 (calcd for C96H91N11O6RuZnPF6 (M - PF6)+
1806).
Ruthenium(II) [5-(4′-Ethynyl-(2,2′;6′,2′′-terpyridinyl))-10,20-
bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)-
(2,2′;6′,2′′-terpyridine)2+ Bis-hexafluorophosphate ([Ru-PZn], 1).
[5-Ethynyl-10,20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)phenyl)-
porphinato]zinc(II) (193 mg, 0.20 mmol), ruthenium(II) (4′-bromo-
2,2′;6′,2′′-terpyridinyl)(2,2′;6′,2′′-terpyridinyl) bis-hexafluorophosphate
(Ru(tpy)2Br) (200 mg, 0.21 mmol), diisopropylamine (8 mL), THF (30
mL), and acetonitrile (30 mL) were brought together in an oven-dried
100-mL Schlenk tube. The solution was degassed via three freeze-
pump-thaw cycles, following which Pd(PPh3)4 (50 mg, 0.04 mmol)
and CuI (10 mg, 0.05 mmol) were added. The reaction was stirred
under N2 at 70 °C for 24 h, the solution was cooled to room temperature,
and the solvent was evaporated. The product was purified by column
chromatography on silica using 80:17:3 acetonitrile/water/saturated
KNO3 as the eluant. Compound 1 eluted as a brownish-green band;
the volume of the product fraction was reduced to 50 mL, and
ammonium hexafluorophosphate (1 g) in 10 mL of water was added,
producing a brown precipitate. The product was filtered, washed
successively with water and ether, and dried to give 250 mg of
compound 1 as the hexafluorophosphate salt (68% yield, based on 193
mg of the [5-ethynyl-10,20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)phe-
1
nyl)porphinato]zinc(II) starting material). H NMR (250 MHz, CD3-
CN): 10.15 (s, 1H), 9.99 (d, 2H, J ) 4.7 Hz), 9.36 (s, 2H), 9.28 (d,
2H, J ) 4.5 Hz), 9.00 (d, 2H, J ) 4.6 Hz), 8.82 (d, 2H, J ) 4.5 Hz),
8.78 (d, 4H, J ) 8.2 Hz), 8.52 (d, 2H, J ) 8.0 Hz), 8.45 (t, 1H, J )
8.5 Hz), 7.97 (t, 2H, J ) 8.2 Hz), 7.94 (t, 2H, J ) 8.2 Hz), 7.81 (t, 2H,
J ) 8.4 Hz), 7.56 (d, 2H, J ) 5.3 Hz), 7.41 (d, 2H, J ) 5.3 Hz), 7.2
(m, 4H), 7.17 (d, 4H, J ) 8.5 Hz), 3.98 (t, 8H, J ) 7.1Hz), 0.76 (t,
8H, J ) 7.0 Hz), 0.19 (s, 36H). LRMS (ESI+) m/z: 1659.4 (calcd for
C88H88N10O4-
Osmium(II) [5-(4′-Ethynyl-(2,2′;6′,2′′-terpyridinyl))-15-(4′-nitro-
phenyl)ethynyl-10,20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)phenyl)-
porphinato]zinc(II)-(2,2′;6′,2′′-terpyridine)2+ Bis-hexafluorophos-
phate ([Os-PZn-A], 4). [5-[(4′-Nitrophenyl)ethynyl]-15-ethynyl-10,20-
bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II) (177
mg, 0.16 mmol), Os(tpy)2Br (300 mg, 0.29 mmol), diisopropylamine
(5 mL), THF (20 mL), and acetonitrile (30 mL) were brought together
in an oven-dried 100-mL Schlenk tube. The solution was degassed via
three freeze-pump-thaw cycles, following which Pd(PPh3)4 (80 mg,
0.07 mmol) and CuI (30 mg, 0.16 mmol) were added. The reaction
was stirred under N2 at 70 °C for 24 h, the solution was cooled to
room temperature, and the solvent was evaporated. The product was
purified by column chromatography on silica using 80:17:3 acetonitrile/
water/saturated KNO3 as the eluant. The product eluted as a brownish-
green band; the volume of the product fraction was reduced to 50 mL,
and ammonium hexafluorophosphate (1 g) in 10 mL of water was
added, producing a brown precipitate. The product was filtered, washed
successively with water and ether, and dried to give 215 mg of
compound 4 as the hexafluorophosphate salt (66% yield, based on 177
mg of the [5-[(4′-nitrophenyl)ethynyl]-15-ethynyl-10,20-bis(2′,6′-bis-
(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II) starting material).
1H NMR (250 MHz, CD3CN): 9.92 (d, 2H, J ) 4.5 Hz), 9.37 (s, 2H),
9.23 (d, 2H, J ) 4.4 Hz), 8.94 (d, 2H, J ) 4.7 Hz), 8.79 (m, 6H), 8.51
(d, 2H, J ) 8.1 Hz), 7.99 (t, 1H, J ) 8.2 Hz), 7.84 (m, 6H), 7.44 (d,
2H, J ) 5.4 Hz), 7.31 (d, 2H, J ) 5.3 Hz), 7.24 (d, 4H, J ) 8.5 Hz),
7.13 (m, 6H), 6.69 (d, 2H, J ) 8.2 Hz), 4.08 (t, 8H, J ) 7.3 Hz), 0.98
(t, 8H, J ) 7.2 Hz), 0.32 (s, 36H). MS (MALDI-TOF) m/z: 1750 (calcd
for C96H91N11O6OsZn (M - 2PF6)+ 1749).
Ru1ZnP2F12 (M - PF6)+ 1659.5). m/z: 757.3 (calcd for C88H88N10O4-
Ru1Zn (M - 2PF6)2+ 758.8).
Osmium(II) [5-(4′-Ethynyl-(2,2′;6′,2′′-terpyridinyl))-10,20-bis-
(2′,6′-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)-
(2,2′;6′,2′′-terpyridine)2+ Bis-hexafluorophosphate ([Os-PZn], 2).
[5-Ethynyl-10,20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)phenyl)-
porphinato]zinc(II) (192 mg, 0.20 mmol), osmium(II) (4′-bromo-
2,2′;6′,2′′-terpyridinyl)(2,2′;6′,2′′-terpyridinyl)bis-hexafluorophos-
phate (Os(tpy)2Br) (215 mg, 0.21 mmol), diisopropylamine (6 mL),
THF (30 mL), and acetonitrile (30 mL) were brought together in an
oven-dried 100-mL Schlenk tube. The solution was degassed via three
freeze-pump-thaw cycles, following which Pd(PPh3)4 (50 mg, 0.04
mmol) and CuI (10 mg, 0.05 mmol) were added. The reaction was
stirred under N2 at 70 °C for 24 h, the solution was cooled to room
temperature, and the solvent was evaporated. The product was puri-
fied by column chromatography on silica using 80:17:3 acetonitrile/
water/saturated KNO3 as the eluant. The product eluted as a brownish-
green band; the volume of the product fraction was reduced to 50 mL,
and ammonium hexafluorophosphate (1 g) in 10 mL of water was
added, producing a brown precipitate. The product was filtered, washed
successively with water and ether, and dried to give 80 mg of com-
pound 2 as the hexafluorophosphate salt (21% yield based on 192
mg of the [5-ethynyl-10,20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)-
phenyl)porphinato]zinc(II) starting material). 1H NMR (250 MHz,
CD3CN): 10.11 (s, 1H), 10.00 (d, 2H, J ) 4.6 Hz), 9.38 (s, 2H),
9.27 (d, 2H, J ) 4.4 Hz), 8.99 (d, 2H, J ) 4.6 Hz), 8.81 (d, 2H, J )
4.3 Hz), 8.75 (m, 4H), 8.48 (d, 2H, J ) 8.1 Hz), 7.97 (t, 1H, J ) 8.2
Hz), 7.84 (m, 4H), 7.78 (t, 2H, J ) 8.4 Hz), 7.75 (m, 4H), 7.41 (d, 2H,
J ) 5.6 Hz), 7.29 (d, 2H, J ) 5.1 Hz), 7.17 (d, 4H, J ) 8.5 Hz), 7.12
(4H, m), 3.99 (t, 8H, J ) 7.1 Hz), 0.78 (t, 8H, J ) 7.1 Hz), 0.18 (s,
36H). LRMS (ESI+) m/z: 1604.4 (calcd for C88H88N10O4OsZn (M -
2PF6)+ 1604.6). m/z: 802.2 (calcd for C88H88N10O4OsZn (M - 2PF6)2+
802.2).
Ruthenium(II) [5-(4′-Ethynyl-(2,2′;6′,2′′-terpyridinyl))osmium-
(II)-15-(4′-ethynyl-(2,2′;6′,2′′-terpyridinyl))-10,20-bis(2′,6′-bis(3,3-
dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)-bis(2,2′;6′,2′′-terpy-
ridine)4+ Tetrakis-hexafluorophosphate ([Ru-PZn-Os], (5). Ru-
thenium(II) [5-(4′-Ethynyl-(2,2′;6′,2′′-terpyridinyl))-15-ethynyl-10,20-
bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)-
(2,2′;6′,2′′-terpyridine)2+ bis-hexafluorophosphate (226 mg, 0.12 mmol),
Os(tpy)2Br (363 mg, 0.35 mmol), diisopropylamine (6 mL), THF (30
9
13808 J. AM. CHEM. SOC. VOL. 124, NO. 46, 2002

(Polypyridyl)metal−(Porphinato)zinc(II) Chromophores
A R T I C L E S
mL), and acetonitrile (100 mL) were brought together in an oven-dried
350-mL Schlenk tube. The solution was degassed via three freeze-
pump-thaw cycles, following which Pd(PPh3)4 (60 mg, 0.05 mmol)
and CuI (15 mg, 0.08 mmol) were added. The reaction was stirred
under N2 at 70 °C for 24 h, the solution was cooled to room temperature,
and the solvent was evaporated. Compound 5 was purified by column
chromatography on silica using 80:17:3 acetonitrile/water/saturated
KNO3 as the eluant. Electronic absorption spectroscopy determined that
the product eluted after several minor fractions as a brown band. The
volume of the product fraction was reduced to 50 mL, and ammonium
hexafluorophosphate (1 g) in 10 mL of water was added, giving a brown
precipitate. The product was filtered, washed successively with water
and ether, and dried to give 76 mg of compound 5 as the hexafluoro-
phosphate salt (23% yield based on 226 mg of the ruthenium(II)
5-[4′-ethynyl-(2,2′;6′,2′′-terpyridinyl)]-15-(ethynyl)bis[10,20-bis(2′,6′-bis-
(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)-(2,2′;6′,2′′-ter-
1
pyridine)2+ bis-hexafluorophosphate starting material). H NMR (250
MHz, CD3CN): 9.98 (d, 2H, J ) 4.6 Hz), 9.97 (d, 2H, J ) 4.7 Hz),
9.39 (s, 2H), 9.38 (s, 2H), 8.95 (d, 2H, J ) 4.5 Hz), 8.94 (d, 2H, J )
4.6 Hz), 8.80 (m, 8H), 8.50 (m, 7H), 7.78 (m, 13H), 7.56 (d, 2H, J )
5.6 Hz), 7.30 (m, 14H), 4.03 (t, 8H, J ) 7.0 Hz), 0.85 (t, 8H, J ) 7.0
Hz), 0.20 (s, 36H). MS (MALDI-TOF) m/z: 2483 (calcd for
C
C
C
120H108N16O4OsRuZnP2F12 (M - 2PF6)+ 2483). m/z: 2339 (calcd for
120H108N16O4OsRuZnPF6 (M - 3PF6)+ 2338). m/z: 2194 (calcd for
120H108N16O4OsRuZn (M - 4PF6)+ 2194).
[5-(4′-Ethynyl-2,2′;6′,2′′-terpyridyl)-10,20-bis(2′,6′-bis(3,3-dimethyl-
1-butyloxy)phenyl)porphinato]zinc(II) (6). [5-Ethynyl-10,20-bis(2′,6′-
bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II) (155 mg, 0.16
mmol), 4′-bromo-2,2′;6′,2′′-terpyridine (280 mg, 0.90 mmol), diiso-
propylamine (8 mL), and THF (30 mL) were brought together in an
oven-dried 100 mL-Schlenk tube. The solution was degassed via three
freeze-pump-thaw cycles, following which Pd(PPh3)4 (30 mg, 0.026
mmol) and CuI (8 mg, 0.042 mmol) were added. The reaction was
stirred under N2 at 70 °C for 20 h, the solution was cooled to room
temperature, and the solvent was evaporated. The product was purified
by column chromatography on neutral alumina using 3:2 hexanes/THF
as the eluant. The product eluted as a green band; the volatiles were
evaporated, and the residual solid was further purified on a size
exclusion column (SX-1 biobeads), utilizing a THF eluant. A second
round of chromatography on neutral alumina using 1:1 THF/hexanes
as the eluant gave 96 mg of pure compound 6 (51% yield based on
155 mg of the [5-ethynyl-10,20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)-
phenyl)porphinato]zinc(II) starting material). 1H NMR (250 MHz,
pyridine-d5) 10.14 (s, 1H), 10.08 (d, 2H, J ) 4.5 Hz), 9.36 (d, 2H, J
) 4.6 Hz), 9.34 (d, 2H, J ) 4.5 Hz), 9.31 (s, 2H), 9.36 (d, 2H, J ) 4.4
Hz), 8.89 (m, 4H), 8.06 (t, 2H, J ) 8.3 Hz), 7.94 (dt, 2H, J ) 7.7 Hz,
1.9 Hz), 7.38 (m, 6H), 4.13 (t, 8H, J ) 7.1 Hz), 0.93 (t, 8H, J ) 7.5
Hz), 0.33 (s, 36H).
Figure 1. Comparative electronic absorption spectra of (A) Ru-PZn,
Os-PZn; (B) Ru-PZn-A, Os-PZn-A; and (C) Ru-PZn-Os, D-PZn-A. Dashed
vertical lines indicate the wavelengths corresponding to the respective second
harmonics of the fundamental 800, 1064, and 1300 nm incident irradiation.
Experimental conditions: T ) 20 °C; solvent ) CH3CN (Ru/Os-containing
compounds), THF (D-PZn-A). R ) 2′,6′-bis(3,3-dimethyl-1-butyloxy)-
phenyl, R′ ) phenyl.
rial). 1H NMR (250 MHz, pyridine-d5) 10.01 (d, 4H, J ) 4.5 Hz), 9.30
(s, 4H), 9.25 (d, 4H, J ) 4.5 Hz), 8.90 (8H, m), 8.08 (t, 2H, J ) 8.3
Hz), 7.94 (dt, 4H, J ) 7.7 Hz, 1.9 Hz), 7.40 (8H, m), 4.18 (t, 8H, J )
7.5 Hz), 0.99 (t, 8H, J ) 7.5 Hz), 0.36 (s, 36H).
Results and Discussion
Design. Figure 1 highlights a series of bis- and tris-
(chromophoric) supermolecules consisting of (porphinato)zinc-
(II) [P(Zn)], Ru(tpy)2, and Os(tpy)2 units in which an ethynyl
moiety bridges the meso-macrocycle and 4′-terpyridyl positions.
These species were synthesized from porphyrinic and terpyridyl
precursor molecules bearing either ethynyl or bromo functional
groups via metal-catalyzed cross-coupling reactions.6,24-37 Key
[5,15-Bis(4′-ethynyl-2,2′;6′,2′′-terpyridyl)-10,20-bis(2′,6′-bis(3,3-
dimethyl-1-butyloxy)phenyl)porphinato]zinc(II) (7). [5,15-Diethynyl-
10,20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc-
(II) (123 mg, 0.13 mmol), 4′-bromo-2,2′;6′,2′′-terpyridine (330 mg, 1.06
mmol), diisopropylamine (8 mL), and THF (30 mL) were brought
together in an oven-dried 100-mL Schlenk tube. The solution was
degassed via three freeze-pump-thaw cycles, following which
Pd(PPh3)4 (30 mg, 0.026 mmol) and CuI (10 mg, 0.053 mmol) were
added. The reaction was stirred under N2 at 70 °C for 20 h, the solution
was cooled to room temperature, and the solvent was evaporated. The
product was purified by column chromatography on neutral alumina
using 7:3 hexanes/THF as the eluant. The product eluted as a purplish-
green band; the volatiles were evaporated, and the residual solid was
further purified on a size exclusion column (SX-1 biobeads), utilizing
a THF eluant. A second round of chromatography on neutral alumina
using 3:2 hexanes/THF as the eluant gave 118 mg of pure compound
7 (63% yield based on 123 mg of the [5,15-diethynyl-10,20-bis(2′,6′-
bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II) starting mate-
(24) Heck, R. F. Acc. Chem. Res. 1979, 12, 146-151.
(25) Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara, N. Synthesis 1980,
627-630.
(26) Kumada, M. Pure Appl. Chem. 1980, 52, 669-678.
(27) Negishi, E.-I.; Luo, F. T.; Frisbee, R.; Matsushita, H. Heterocycles 1982,
18, 117-122.
(28) Stille, J. K. Angew. Chem., Int. Ed. Engl. 1986, 25, 508-524.
(29) Miyaura, N.; Suzuki, A. Chem. ReV. 1995, 95, 2457-2483.
(30) DiMagno, S. G.; Lin, V. S. Y.; Therien, M. J. J. Am. Chem. Soc. 1993,
115, 2513-2515.
(31) DiMagno, S. G.; Lin, V. S. Y.; Therien, M. J. J. Org. Chem. 1993, 58,
5983-5993.
(32) Lin, V. S. Y.; Therien, M. J. Chem.sEur. J. 1995, 1, 645-651.
(33) LeCours, S. M.; Guan, H. W.; DiMagno, S. G.; Wang, C. H.; Therien, M.
J. J. Am. Chem. Soc. 1996, 118, 1497-1503.
(34) LeCours, S. M.; DiMagno, S. G.; Therien, M. J. J. Am. Chem. Soc. 1996,
118, 11854-11864.
(35) LeCours, S. M.; Phillips, C. M.; de Paula, J. C.; Therien, M. J. J. Am.
Chem. Soc. 1997, 119, 12578-12589.
9
J. AM. CHEM. SOC. VOL. 124, NO. 46, 2002 13809

A R T I C L E S
Uyeda et al.
Scheme 1
design elements of these species exploit the facts that (1)
ruthenium polypyridyl compounds possess significant optical38
nonlinearities, outstanding thermal stabilities,39-42 and electroni-
cally excited states characterized by multidirectional metal-to-
ligand charge transfer (MLCT);43 (2) appropriate polypyridyl
ethyne derivatization gives rise to a singly degenerate, low-
energy electronically excited CT state; and (3) coupling such
an ethynylated metal polypyridyl moiety to a PZn meso-carbon
position enforces a head-to-tail alignment of the corresponding
transition dipoles of the two chromophoric entities,6,32-37,44,45
defining a supermolecular structure having an initially prepared
singly degenerate excited state polarized along this vector.
Synthesis. The syntheses of these ethyne-bridged (porphi-
nato)zinc-bis(terpyridyl)metal compounds are summarized in
Scheme 1. The metal-mediated cross-coupling6,24-37 of an
6,30-37
ethyne-functionalized (porphinato)zinc(II) species
with
appropriately halogenated bis(2,2′;6′,2′′-terpyridyl)metal com-
pounds provides entry into this structural class of supermolecular
chromophores. These structures contrast conventional covalently
linked porphyrin-polypyridyl(metal) assemblies46-50 in that a
cylindrically π-symmetric bridge directly links the two chro-
mophores.
(36) Shediac, R.; Gray, M. H. B.; Uyeda, H. T.; Johnson, R. C.; Hupp, J. T.;
Angiolillo, P. J.; Therien, M. J. J. Am. Chem. Soc. 2000, 122, 7017-7033.
(37) Susumu, K.; Therien, M. J. J. Am. Chem. Soc. 2002, 124, 8550-8552.
(38) Vance, F. W.; Hupp, J. T. J. Am. Chem. Soc. 1999, 121, 4047-4053.
(39) Dhenaut, C.; Ledoux, I.; Samuel, I. D. W.; Zyss, J.; Bourgault, M.; Lebozec,
H. Nature (London) 1995, 374, 339-342.
The Ru-PZn and Os-PZn complexes were prepared by the
respective cross-coupling of the 4′-halogenated metal bis-
(terpyridyl) compounds Ru(tpy)2Br and Os(tpy)2Br with 5-ethy-
nyl-10,20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]-
(40) Morrison, I. D.; Denning, R. G.; Laidlaw, W. M.; Stammers, M. A. ReV.
Sci. Instrum. 1996, 67, 1445-1453.
(41) (a) Warachim, H.; Bujewski, A. J. Therm. Anal. 1984, 29, 1001-1004.
(b) Schro¨der, M.; Stephenson, T. A. ComprehensiVe Coordination Chem-
istry; Wilkinson, G. F., Gillard, R. D., McCleverty, J. A., Eds.; Pergamon:
Oxford, U.K., 1987; Vol. 4, pp 277-522.
(42) TGA-DTA studies indicate that Td for Ru-PZn exceeds 325 °C, consistent
with literature precedent (see refs 33 and 41).
(44) Kumble, R.; Palese, S.; Lin, V. S. Y.; Therien, M. J.; Hochstrasser, R. M.
J. Am. Chem. Soc. 1998, 120, 11489-11498.
(45) Angiolillo, P. J.; Lin, V. S. Y.; Vanderkooi, J. M.; Therien, M. J. J. Am.
Chem. Soc. 1995, 117, 12514-12527.
(43) Damrauer, N. H.; Cerullo, G.; Yeh, A.; Boussie, T. R.; Shank, C. V.;
McCusker, J. K. Science (Washington D. C.) 1997, 275, 54-57.
9
13810 J. AM. CHEM. SOC. VOL. 124, NO. 46, 2002

(Polypyridyl)metal−(Porphinato)zinc(II) Chromophores
A R T I C L E S
Table 1. Electronic Spectral Data for Ru-PZn, Os-PZn, Ru-PZn-A, Os-PZn-A, and Ru-PZn-Os and Chromophoric Benchmarks 6-11
abs band maxima (nm) (ꢀ × 10-5 [M-1 cm-1])
Q-state
transitions
oscillator strength
B-band region
oscillator strength
Q-band region
total oscillator
strength
compd
B-band
MLCT
3MLCT
Ru-PZn
428
(1.07)
425
506
(0.56)
498
567
(0.15)
561
639
(0.51)
675
2.10e,j
2.43e,j
0.27f
0.42f
2.37g
2.85g
Os-PZn
(1.12)
440
(1.10)
459
(0.56)
(0.21)
641
(0.36)
625
(0.30)
Ru-PZn-A
504
682
2.04e,j
2.53e,j
3.38h,j
1.89e
2.04e
1.39a
2.34a
0.41f
0.62f
0.79i
0.17f
0.30f
0.08b
0.16b
2.45g
3.15g
4.17g
2.06g
2.34g
1.47c
2.50c
0.31d
0.24d
(1.47)
459
(1.68)
456
(1.28)
441
(3.86)
454
(4.88)
430
(2.92)
438
(0.55)
499
(0.71)
509
(0.16)
573
(0.14)
573
(0.22)
567
(0.16)
(0.79)
702
(0.87)
715
(1.16)
618
(0.26)
659
(0.66)
606
(0.07)
634
Os-PZn-A
Ru-PZn-Os
(1.27)
6
7
8
563
(0.12)
580
9
(3.82)
(0.12)
(0.29)
10
11
483
(0.20)
482
665
(0.16)
(0.04)
a Oscillator strengths calculated over the 290 f 480 wavelength domain. b Oscillator strengths calculated over the 480 f 850 wavelength domain. c Oscillator
strengths calculated over the 290 f 850 wavelength domain. d Oscillator strengths calculated over the 380 f 850 wavelength domain. e Oscillator strengths
calculated over the 360 f 555 wavelength domain. f Oscillator strengths calculated over the 555 f 850 wavelength domain. g Oscillator strengths calculated
over the 360 f 850 wavelength domain. h Oscillator strengths calculated over the 360 f 600 wavelength domain. i Oscillator strengths calculated over the
600 f 850 wavelength domain. j Includes contributions from metal polypyridyl-derived transitions.
zinc(II) (Scheme 1). Ru-PZn-A and Os-PZn-A were prepared
in a similar fashion, utilizing a PZn intermediate featuring
5-ethynyl and 15-(nitrophenyl)ethynyl substituents (Scheme 1).
Ru-PZn-Os was prepared in a stepwise manner in which a 4′-
ethynyl ruthenium bis(terpyridyl) compound was cross-coupled
to a PZn complex functionalized with 5-triisopropylsilylethynyl
and 15-bromo substituents. Removal of the triisopropylsilyl pro-
tecting group followed by a second cross-coupling with osmium-
(II) (4′-bromo-2,2′;6′,2′′-terpyridinyl)(2,2′;6′,2′′-terpyridinyl)-
bis-hexafluorophosphate, gave the desired complex (Scheme 1).
Compounds Ru-PZn, Os-PZn, Ru-PZn-A, Os-PZn-A, and
Ru-PZn-Os were isolated via column chromatography on silica
using CH3CN/H2O/saturated KNO3 as the eluant. Purification
of key precursor compounds [5-(4′-ethynyl-2,2′;6′,2′′-terpyri-
dyl)-10,20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)phenyl)porphi-
nato]zinc(II) (6) and [5,15-bis(4′-ethynyl-2,2′;6′,2′′-terpyridyl)-
10,20-bis(2′,6′-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]-
zinc(II) (7) (Scheme 1) utilized neutral alumina as the chro-
matographic stationary phase. Ru-PZn, Os-PZn, Ru-PZn-A,
Os-PZn-A, and Ru-PZn-Os were isolated as their hexafluoro-
phosphate salts via metathesis reactions.
with metal polypyridyl charge-resonance bands and display a
variety of new low energy electronic transitions that feature
significant µ2 values and large extinction coefficients. Two
ge
aspects of these electronic spectra (Figure 1) are particularly
noteworthy: (i) they differ markedly from those characteristic
of monomeric ethyne-elaborated PZn and Ru(tpy)2 chro-
mophores (Supporting Information),6,32-36,51,52 and (ii) they
display an unusual degree of spectral coverage of the 250-750
nm energy domain. In this latter regard, note that the extinction
coefficient of Ru-PZn-Os’s absorption minimum over this wave-
length range (at ∼ 610 nm) exceeds 15 000 M-1 cm-1. Table
1 lists the spectral data for these compounds, along with that
obtained for key functionalized chromophoric precursor mol-
ecules 6, 7, [5-triisopropylsilylethynyl-10,20-bis(2′,6′-bis(3,3-
dimethyl-1-butyloxy)phenyl)porphinato]zinc(II) (8), [5,15-
bis-trimethylsilylethynyl-10,20-di(2′,6′-bis(3,3-dimethyl-1-
butyloxy)phenyl)porphinato]zinc(II) (9), [Ru(tpy)(4′-trimethyl-
silylethynyl-tpy)](PF6)2 (10), and [Os(tpy)(4′-trimethylsilyleth-
ynyl-tpy)](PF6)2 (11); optical spectra of these chromophoric
benchmarks are contained within the Supporting Information.
The optical spectra of compounds 6 and 7 contrast with
those obtained for Ru-PZn, Os-PZn, Ru-PZn-A, Os-PZn-A, and
Ru-PZn-Os; note that the electronic absorption spectra of meso-
ethynyl-terpyridine functionalized PZn compounds 6 and 7
(Supporting Information) resemble those reported previously for
5- and [5,15-di(arylethynyl)porphinato]zinc(II) complexes,33-35,53
indicating that the building block Ru/Os- and ligand-derived
electronic transitions figure prominently in the coupled oscil-
Electronic Absorption Spectroscopy. Consistent with the
design features of Ru-PZn, Os-PZn, Ru-PZn-A, Os-PZn-A, and
Ru-PZn-Os noted above, the electronic spectra of these species
(Figure 1) evince strong mixing of PZn-based oscillator strength
(46) Harriman, A.; Odobel, F.; Sauvage, J. P. J. Am. Chem. Soc. 1994, 116,
5481-5482.
(47) Collin, J.-P.; Harriman, A.; Heitz, V.; Odobel, F.; Sauvage, J.-P. J. Am.
Chem. Soc. 1994, 116, 5679-5690.
(48) Harriman, A.; Odobel, F.; Sauvage, J.-P. J. Am. Chem. Soc. 1995, 117,
9461-9472.
(51) Sauvage, J. P.; Collin, J. P.; Chambron, J. C.; Guillerez, S.; Coudret, C.;
Balzani, V.; Barigelletti, F.; De Cola, L.; Flamigni, L. Chem. ReV. 1994,
94, 993-1019.
(52) Gouterman, M. J. Mol. Spectrosc. 1961, 6, 138-163.
(53) Karki, L.; Vance, F. W.; Hupp, J. T.; LeCours, S. M.; Therien, M. J. J.
Am. Chem. Soc. 1998, 120, 2606-2611.
(49) Flamigni, L.; Barigelletti, F.; Armaroli, N.; Ventura, B.; Collin, J. P.;
Sauvage, J. P.; Williams, J. A. G. Inorg. Chem. 1999, 38, 661-667.
(50) Dixon, I. M.; Collin, J.-P.; Sauvage, J.-P.; Barigelletti, F.; Flamigni, L.
Angew. Chem., Int. Ed. 2000, 39, 1292-1295.
9
J. AM. CHEM. SOC. VOL. 124, NO. 46, 2002 13811

A R T I C L E S
Uyeda et al.
Table 3. Oxidative and Reductive Cyclic Voltammetric Dataa for
Table 2. Dynamic Hyperpolarizabilities [âλ Values, (× 10-30 esu)]
Determined via HyperRayleigh Light Scattering Experimentsa
Ru-PZn, Os-PZn, Ru-PZn-A, Os-PZn-A, and Ru-PZn-Os and
Potentiometric Benchmarks 8-11
b
compd
â
â1064
â1300
∼800
potentiometric data (mV)
Ru-PZn
Os-PZn
Ru-PZn-A
Os-PZn-A
Ru-PZn-Os
D-PZn-A
<50c
<50c
220
2100
2600
4000
5000
4500
4933d
5100
<50c
2400
<50c
860
+
+
2+
2+ 3+
0
compd
ZnP/ZnP ZnP /ZnP
M /M
tpy-/tpy0 ZnP-/ZnP tpy2-/tpy-
Ru-PZn
Os-PZn
Ru-PZn-A
870
845
910
900
1130
1075b
1150
1210
1465 -1065 -1365 -1575
1075b -1040 -1340 -1575
250
240
1430
1090
-990 -1260
-990 -1230
5142d
e
Os-PZn-A
Ru-PZn-Osc
a Conditions: T ) 20 °C, solvent ) CH2Cl2. âλ values reported are
independent of the frequency modulation of the fundamental beam (DC
to 960 MHz; see exemplary data in Figure 2), indicating that multipho-
ton fluorescence contributions to the observed HRS signals are absent.
See refs 22, 23, 54, 55, and 64. b Dynamic hyperpolarizabilities deter-
mined at λinc ) 800 nm for Ru-PZn, Os-PZn, Ru-PZn-A, Os-PZn-A, and
Ru-PZn-Os and at λinc ) 830 nm for D-PZn-A. c Upper limit corresponds
to the smallest HRS signal that can be measured accurately. d See ref 33.
e Not measured.
8
9
10
11
765
820
965
1300
-1420
-1230
1275 -1145
950 -1115
-1445
-1420
-1840b
a Experimental conditions: [chromophore] ) 1-3 mM; scan rate ) 0.5
V/s; reference electrode ) Ag wire. E1/2 values reported are relative to
SCE; the ferrocene/ferrocenium couple (0.43 V vs SCE) was used as the
internal standard. Potentiometric data for compounds 8-11 were obtained
in 0.1 M TBABF4/dimethylformamide, while that for Ru-PZn, Os-PZn,
Ru-PZn-A, Os-PZn-A, and Ru-PZn-Os utilized a 0.1 M TBAPF6/dichlo-
romethane electrolyte/solvent system. The experimental uncertainty in these
reported potentials is (10 mV. All reported values correspond to one
electron redox couples unless noted otherwise. b The OsII/OsIII and the ZnP+/
ZnP2+ redox couples appear to be coincident or near coincident. c Compound
Ru-PZn-Os exhibited complex and irreversible redox behavior in the solvent/
electrolyte systems listed above.
lator photophysics manifest by the Ru-PZn, Os-PZn, Ru-PZn-
A, Os-PZn-A, and Ru-PZn-Os supermolecules.
Nonlinear Optical Properties. Table 2 lists âλ values for
Ru-PZn, Os-PZn, Ru-PZn-A, Os-PZn-A, and Ru-PZn-Os de-
termined from hyperRayleigh light scattering (HRS) measure-
ments22,54,55 and highlights the frequency dependence of the
NLO response observed for fundamental incident irradiation
wavelengths (λinc) of 800, 1064, and 1300 nm. Tabulated here
as well are analogous HRS data obtained for the benchmark
PZn-based NLO chromophore 5-(4′-dimethylaminophenylethy-
nyl)-15-(4”-nitrophenylethynyl)-10,20-diphenylporphinato]zinc-
(II) (D-PZn-A) (Figure 1C), a high µâ0 pigment which possesses
â830 and â1064 values near 5000 × 10-30 esu, a â1906 value of
1000 × 10-30 esu, and a static hyperpolarizability (â0) of ∼800
× 10-30 esu.33,53,56
2, the nature of the extensive mixing of B, Q, and CT electronic
states evinced for Ru-PZn, Os-PZn, Ru-PZn-A, Os-PZn-A, and
Ru-PZn-Os in Figure 1 is considerably more complex relative
to that manifested in D-PZn-A: this derives from the fact that
these species possess at least three redox active components
(metal, tpy, and PZn). Potentiometric data for these compounds
are listed in Table 3.
The oxidative and reductive electrochemical data indicate that
at least for Ru-PZn, Os-PZn, Ru-PZn-A, and Os-PZn-A, the
observed anodic and cathodic potentiometric responses trace
their genesis to established metal polypyridyl- and PZn-redox
processes, indicating that the singly, doubly, and triply oxidized-
and reduced-ground states of these species correspond to cation
and anion states that are largely localized on the building block
chromophores (Table 3). These potentiometric data permit a
preliminary analysis of the observed frequency dispersion effects
in the NLO response of these species.
The trends observed in Table 2 are unusual. For example,
the HRS data show that while for Ru-PZn, the absolute
magnitude of the dynamic hyperpolarizability (|âλ|) increases
with increasing λinc (800 f 1064 f 1300 nm), structurally
related Os-PZn displays a |âλ| maximum at 1064 nm and âλs
< 50 × 10-30 esu at 800 and 1300 nm. Ru-PZn-A and
Ru-PZn-Os express modest âλ values for incident irradiation at
800 nm, large âλs at 1064 nm, and âλs of 2400 and 860 × 10-30
esu, respectively, at 1300 nm. The λinc-dependent trend in âλ
values for Os-PZn-A resembles that observed for Os-PZn, with
the large observed â1064 value diminishing to approximately zero
at λinc ) 1300 nm.
The λinc-dependent trend in âλ values for D-PZn-A is well
understood.33,53,56 It derives from the expected resonance
enhancement effects and the facts that both the x-polarized
porphyrin B and Q states possess identical CT character and
âïs of the same sign; âλ contributions from the B- and Q-derived
transitions thus have opposite signs when two-photon resonance
frequencies lie between the B- and Q-derived transitions (e.g.,
when λinc ) 1064 nm). Similar nonlinear optical behavior has
been noted in (dicyanomethylene)pyran chromophores, in which
two low lying CT transitions contribute to the static hyperpo-
larizability.57 While NLO response frequency dispersion effects
driven by the presence of multiple CT transitions undoubtedly
play a role in determining the magnitudes of âλ listed in Table
A qualitative analysis of the nature of the x-polarized
transitions in Ru-PZn and Os-PZn, based on potentiometric data
and the Gibbs free energy relation, suggests that B- and Q-state
∆µge values have opposite signs: M(tpy)2-to-PZn charge
resonance is thermodynamically favored with B-state excitation,
while PZn-to-M(tpy)2 CT occurs with excitation of the x-
polarized Q state.58 Because B- and Q-state â0s would thus have
opposite signs when the expected resonance enhancements
effects predicted in a classic 2-level formulation of â (eq 1)59-61
(57) Moylan, C. R.; Ermer, S.; Lovejoy, S. M.; McComb, I. H.; Leung, D. S.;
Wortmann, R.; Krdmer, P.; Twieg, R. J. J. Am. Chem. Soc. 1996, 118,
12950-12955.
(58) -(∆GCS) ) E(0,0) - E1/2(D/D+) + E1/2(A-/A), where E(0, 0) is the two-photon
resonance energy and the E1/2(D/D+) and E1/2(A-/A) values were determined
from cyclic voltammetric data (see Table 3). Ru-PZn: Ru2+/3+ ) 1.47 V,
PZn-/0 ) -1.37 V, Ru(tpy)-/0 ) -1.07 V, PZn0/+ ) 0.87 V. Os-PZn:
Os2+/3+ ) 1.08 V, PZn-/0 ) -1.34 V, Os(tpy)-/0 ) -1.04 V, PZn0/+
)
0.85 V. The nature of the E(0,0)-dependent CT transition was estimated by
approximating -(∆GCS) for all possible charge separations and determining
which was the most thermodynamically favorable under the assumption
that one full unit of charge migrates at these resonance energies. A similar
analysis can be used to rationalize the λinc-dependent HRS data for Ru-
PZn-A, Os-PZn-A, and Ru-PZn-Os.
(54) Terhune, R. W.; Maker, P. D.; Savage, C. M. Phys. ReV. Lett. 1965, 14,
681-684.
(55) Clays, K.; Persoons, A. Phys. ReV. Lett. 1991, 66, 2980-2983.
(56) Priyadarshy, S.; Therien, M. J.; Beratan, D. N. J. Am. Chem. Soc. 1996,
118, 1504-1510.
9
13812 J. AM. CHEM. SOC. VOL. 124, NO. 46, 2002

(Polypyridyl)metal−(Porphinato)zinc(II) Chromophores
A R T I C L E S
6(Pge)2n(∆µge)n(Eop)2n
â′n )
(1)
[(Eop)2n - (2Einc)2][(Eop)2n - Einc
]
2
(where Eop is the energy of the optical transition of interest)
are considered, B- and Q-state derived contributions to âλ will
have the same sign when the two-photon resonance frequencies
lie between the B- and Q-derived transitions and will have
opposite signs at both short and long wavelength, resulting in
a cancellation of the HRS signal when λinc ) 800 and 1300
nm. For both the Ru-PZn and Os-PZn cases, this cancellation
is effectively complete when λinc ) 800 nm. Note that the optical
spectra of Figure 1 along with eq 1 predict qualitatively that
Ru-PZn’s Q-state derived contributions to âλ at 1300 nm will
be large and positive, with the corresponding B-state derived
contribution being small and negative, giving a large net â1300
value. In contrast, while Os-PZn’s B-state derived contribution
to â1300 is also small and negative, note that its Q-state derived
âλ contribution will be small and positive, as near-equivalent
amounts of x-polarized Q-state oscillator strength are dis-
tributed to the blue and the red of the 2-photon absorption at
650 nm (Figure 1), resulting in effective canceling of the HRS
signal when λinc ) 1300 nm. Presumably, for the Os-PZn and
Os-PZn-A systems that exhibit highly diminished HRS signals
at 1300 nm, because the energy denominator (eq 1) increasingly
favors contributions from the lowest energy excited state in a
two-level formulation of the first-order hyperpolarizability as
the zero frequency limit is approached,59,62 these species would
be predicted to manifest modest, finite âλs for longer λinc, given
the nature and extensive oscillator strength of their respective
Q-derived transitions. Because of the complex electronic
structure of the Ru-PZn, Os-PZn, Ru-PZn-A, and Os-PZn-A
compounds, a fully quantitative analysis of the frequency
dispersion effects manifest in the NLO responses of these species
will require further spectroscopic experiments, the syntheses of
related derivatives, and substantive theoretical studies; nonethe-
less, the hypothesis based on potentiometric data that B- and
Q-state contributions to the static hyperpolarizability have
opposite signs in these supermolecular chromophores quali-
tatively accounts for the general trends manifest in the
Figure 2. Measured â1300 Values for Ru-PZn Determined as a Function
of Modulation Frequency.
obtained for RuPZn; note that the measured HRS signal is
constant up to 1 GHz, showing conclusively that the large â1300
value of 5100 × 10-30 esu (Table 2) is not overestimated
because of multiphoton fluorescence.
Conclusions
In summary, this work highlights that: (i) Coupled oscillator
photophysics65 and metal-mediated cross-coupling can be
exploited to elaborate high â0 supermolecules. (ii) High-stability
metal polypyridyl compounds constitute an attractive alternative
to electron releasing dialkyl- and diaryl-amino groups, the most
commonly used donor moieties in a wide range of established
NLO dyes and long recognized to be the moiety that often limits
dye thermal stability.41-42,66 (iii) Given the NLO response
highlighted by Ru-PZn and the fact that its âλ value determined
at 1300 nm exceeds by a factor of 2.5 that determined for any
other chromophore at this energy,67 this design strategy clearly
enables ready elaboration of extraordinarily large âλ chro-
mophores at telecommunication-relevant wavelengths. (iv) An
important new effect has been delineated in this series of
compounds, namely that B- and Q-state-derived â0 values can
be designed to have the same or opposite sign; because the sign
of the resonance enhancement factor is frequency dependent,
appropriate engineering of the relative contributions of these
CT states at a given wavelength provides a new means to
regulate the magnitude of dynamic hyperpolarizabilities and,
thus, may enable the development of novel materials with
enhanced and more selective electrooptic and NLO properties.
λ
inc-dependent magnitudes of |âλ| chronicled in Table 2.
Finally, it is important to emphasize that the large âλ values
listed in Table 2 do not derive in part from multiphoton
fluorescence contributions to the hyperRayleigh scattering signal.
First, it is known that Ru-PZn, Os-PZn, Ru-PZn-A, Os-PZn-A,
and Ru-PZn-Os are all nonemissive at ambient temperature.63
For further experimental proof that multphoton fluorescence
contributions to the HRS signal are indeed absent, HRS
experiments were performed as a function of amplitude modula-
tion frequency up to 1 GHz.22,23,54,55,64 Because of the fact that
fluorescence lifetimes are finite, any fluorescence contribution
would be demodulated at such frequencies and evident experi-
mentally as an HRS signal that decreased with increasing
modulation frequency. Figure 2 shows such exemplary data
Acknowledgment. This work was supported by a grant from
the Office of Naval Research N00014-01-1-0725, the Belgian
Government (IUAP/5/3), the Flemish Fund for Scientific
Research (G.0261.02), and the University of Leuven (G0A/
2000/03).
Supporting Information Available: Syntheses and charac-
terization data for precursor compounds, along with benchmark
optical spectra for the ethyne-elaborated bis(terpyridyl)metal and
(porphinato)zinc(II) building blocks. This material is available
free of charge via the Internet at http://pubs.acs.org.
(59) Oudar, J. L.; Chemla, D. S. J. Chem. Phys. 1977, 66, 2664-2668.
(60) Oudar, J. L. J. Chem. Phys. 1977, 67, 446-457.
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JA020651Q
(65) Toury, T.; Zyss, J.; Cherynak, V.; Mukamel, S. J. Phys. Chem. A 2001,
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M.; Miller, R. D. J. Am. Chem. Soc. 1993, 115, 12599-12600.
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K.; Duan, X.-M. J. Opt. Soc. Am. B 2000, 17, 256-265.
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T.; Therien, M. J. Manuscript in preparation.
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