Chemoselective photochemical surface reaction - Ketene versus carbene reactivity from the photolysis of saturated monolayers of pyridyl diazoesters on single-crystal Pt

Article abstract of DOI:10.1139/V10-113

Irradiation of saturated monolayers of 3-and 4-substituted pyridyl diazoacetates on single-crystal Pt surfaces leads to either the corresponding reactive carbene or stable ketene intermediate with the chemoselectivity determined by the position of the photoreactive substituent on the pyridyl ring, which ultimately directs the available interactions with neighboring substrates.

Full text of DOI:10.1139/V10-113

1
17
Chemoselective photochemical surface
reaction — Ketene versus carbene reactivity from
the photolysis of saturated monolayers of pyridyl
diazoesters on single-crystal Pt
Jason L. Pitters, Dana K. Adkinson, Keith Griffiths, Peter R. Norton, and
Mark S. Workentin
Abstract: Irradiation of saturated monolayers of 3- and 4-substituted pyridyl diazoacetates on single-crystal Pt surfaces
leads to either the corresponding reactive carbene or stable ketene intermediate with the chemoselectivity determined by
the position of the photoreactive substituent on the pyridyl ring, which ultimately directs the available interactions with
neighboring substrates.
Key words: ketene, carbene, diazoester, saturated monolayer, photochemistry, Pt surfaces.
R e´ sum e´ : L’irradiation de monocouches satur e´ es de diazoac e´ tates de pyridyles substitu e´ s dans les positions 3 et 4 sur des
surfaces de monocristaux de platine conduit a` la formation soit du carb e` ne r e´ actif correspondant ou de l’interm e´ diaire c e´ -
t e` ne stable dans lesquels la chimios e´ lectivit e´ est d e´ termin e´ e par la position du substituant photor e´ actif sur le noyau pyri-
dyle qui en fin de compte dirige les interactions disponibles avec les substrats avoisinants.
Mots-cl e´ s : c e´ t e` ne, carb e` ne, diazoester, monocouche satur e´ e, photochimie, surfaces de platine.
[
Traduit par la R e´ daction]
rigid molecular architecture of the base pyridyl rings. Diazo-
esters are known to react thermally and photochemically
with loss of nitrogen to form the corresponding carbene in-
Introduction
The ability to precisely control the reactivity of organic
molecules as saturated monolayers on metal surfaces is a
significant challenge. Results of such studies remain of in-
terest because of the continued need for efficient methods
for the selective chemical modification of the surface for a
4
termediate. Unlike diazoketones or diazoaldehydes, they do
not generally undergo efficient Wolff-type rearrangements
to generate a ketene because of the poor migratory aptitude
of the –OR group; instead, they generally react through a
carbene.4 For example, aryl diazoester derivatives show
1
host of applications. Most studies with these goals concen-
trate on monolayers based on long alkyl chains with surface
active groups bound to Au or Si, while studies of smaller,
less flexible organic molecular architectures are relatively
4c
only traces (<1%) of Wolff rearrangement. Pyridyl diazo-
esters are not well studied, and only in the case of 3-PDE
was the formation of a ketene observed, but this was at 10
unexplored.2,3 Monolayers of smaller and more rigid mole-
5
K in an Ar matrix. In solution, we found 98% of the prod-
cules should allow for more careful control and understand-
ing of the orientation of the organic substrate and allow for
selectivity in the interfacial reactivity as a function of the
position of the reactive moiety on the rigid structure of the
moiety forming the monolayer.
Here, we report a remarkable and unprecedented chemo-
selectivity in a monolayer surface photoreaction, namely the
photoreaction of pyridyl diazoacetates (3- and 4-PDE) on
single-crystal platinum surfaces. The chemoselectivity re-
sults from the relative position of the reactive group on the
ucts from irradiation of 3- or 4-PDE are from trapping of the
6
carbene intermediate. However, in this report, we show that
we can select the reactivity between the carbene and ketene
by simply altering the position of the diazoester function on
the pyridyl ring that is bound to the metal surface
(Scheme 1). Such control sheds important insights into the
reactivity in this type of monolayer environment and sug-
gests that this experimental approach also provides a method
for characterizing reactive intermediates.
Received 1 June 2010. Accepted 22 July 2010. Published on the NRC Research Press Web site at canjchem.nrc.ca on 7 January 2011.
This article is part of a Special Issue dedicated to Professor J. C. Scaiano.
J.L. Pitters. National Institute for Nanotechnology (NINT), National Research Council (NRC) of Canada, 11421 Saskatchewan Drive,
Edmonton, AB T6G 2M9, Canada.
D.K. Adkinson, K. Griffiths, P.R. Norton, and M.S. Workentin. Department of Chemistry, The University of Western Ontario,
1
London, ON N6A 5B7, Canada.
1Corresponding author (e-mail: mworkent@uwo.ca).
Can. J. Chem. 89: 117–121 (2011)
doi:10.1139/V10-113
Published by NRC Research Press

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Can. J. Chem. Vol. 89, 2011
Scheme 1. Chemoselectivity in the surface photochemistry of 3-
and 4-PDE on Pt.
ordered when impurities of carbon, sulfur, and oxygen were
not observed with AES and a sharp LEED pattern was ob-
served.7
The surface photochemical experiments were performed
using a 200 W mercury–xenon arc lamp supplied by Oriel.
The lamp was filtered with a series of mirrors and cut-off
filters to transmit light from 300 to 400 nm. The light en-
tered the UHV chamber through a quartz window and was
focused on the sample through a series of external fused-
silica optical lenses.
Experimental
Methyl diazo(3-pyridyl)acetate (3-PDE)
A procedure adapted from Tomioka et al. was used for
the synthesis of 3-PDE. The compound 3-acetyl pyridine
All ultra-high vacuum (UHV) experiments were per-
formed in a stainless steel chamber pumped with a 330 L
5
–
1
s
turbo molecular pump and a titanium sublimation pump.
(
(
30 g, 0.25 mol) was heated to reflux in morpholine
–10
With these pumps, background pressures in the low 10
37.5 g, 0.43 mol) with sulfur (13 g, 0.41 mol) for 6 h in a
torr range (1 torr = 133.322 Pa) could be achieved. The
chamber was interfaced to a Mattson Cygnus 100 Fourier
transform infrared spectrometer for FTIR–RAIR (reflection
absorption infrared) spectroscopy. The external optical sys-
tem for the RAIRS consisted of a flat plane mirror that re-
directed the collimated IR light from the spectrometer to a
parabolic mirror that focused the light on the sample surface
in the chamber at a grazing angle. The reflected light from
the sample then left the chamber to be re-collimated by an-
other parabolic mirror and then focused on the detector with
a final parabolic mirror. The UHV chamber was fitted with
KCl windows, and a liquid-nitrogen-cooled narrow-band
mercury cadmium telluride detector with a spectral range of
8
modified Willgerodt reaction. The mixture was poured onto
ice and allowed to stand overnight. The resulting crystals
were then filtered and recrystallized from a 50% benzene/
petroleum ether mixture to give a pure thioacetomorpholide
(
63%). The thioacetomorpholide (8 g, 0.036 mol) was
heated to reflux in 80 mL of a 50% ethanol/water mixture
with excess KOH for 12 h. The water and ethanol were re-
moved and the mixture was taken up in methanol (MeOH),
which was acidified with dry HCl. This mixture was then
heated to reflux for 24 h. The MeOH was removed and the
salt was taken up in water and made basic with solid
NaHCO . The resulting pyridyl ester was then extracted
3
with ether and dried with magnesium sulfate and the ether
was removed under vacuum to give a pale yellow liquid.
This liquid was distilled at 100 8C at 0.1 mm Hg (1 mm
Hg = 133.322 Pa) to give a colorless liquid of methyl (3-
pyridyl)acetate (59%). The methyl (3-pyridyl)acetate (2 g,
0.013 mol) was stirred for 3 days at room temperature in
8
00–4000 cm–1 was used for the experiments. The optical
system was purged with dried air and scrubbed of CO with
2
a Balston FTIR gas-purge generator system. A PIKE Tech-
nologies wire grid polarizer was also used to filter out the
s-polarized light. Also interfaced to the UHV chamber was an
+
Ar ion gun, a quadrupole mass spectrometer for temperature-
50 mL acetonitrile with tosyl azide (0.026 mol) and 4 g of
programmed desorption (TPD), and low energy electron dif-
fraction (LEED) optics that could be substituted for an
Auger system with a cylindrical mirror analyzer. Through a
KF/Al O solid support.9,10 The solid support was then fil-
2
3
tered off and the acetonitrile was removed, leaving an or-
ange solid. The solid was chromatographed on silica 60
(80 g silica per 1 g diazoester) with ethyl acetate. The re-
moval of the ethyl acetate left an orange crystal that was
shown to be pure methyl diazo(3-pyridyl)acetate (87%). Mp
58–60 8C. UV–vis (MeCN) lmax, nm (3, L mol–1 cm ): 272
separately pumped gas manifold, Ar for sputtering, O for
2
cleaning, and CO could be introduced to the chamber with
the use of leak valves. Two separate leak valves were also
available for the introduction of samples to the surface for
analysis. Dosing of samples was directed through steel tubes
to the surface to ensure surface coverage without chamber
contamination.
–1
–1
(11800), 248 (12400), 207 (11770). IR (CCl ) n (cm ):
4
3035, 30003, 2955, 2845, 2091 (C=N=N), 1713 (C=O),
1587, 1565, 1481, 1437, 1421, 1360, 1348, 1261, 1195,
The Pt crystal, either Pt(110) or Pt(111), was attached to
the sample mount (two nickel-coated copper posts) by spot-
welding four 0.010 inch (1 inch = 2.54 cm) diameter Pt wire
to the back of the crystal. A K-type thermocouple was spot-
welded to the edge of the crystal for temperature monitor-
ing. The crystal was initially annealed for 3 days at 1073 K
1063, 1032, 1020, 911. 1H NMR (200 MHz, CDCl ) d
3
(ppm): 3.89 (s, 3H), 7.31 (m, 1H), 7.88 (m, 1H), 8.43 (dd,
1H), 8.69 (m, 1H). 13C NMR (50 MHz, CDCl ) d (ppm):
3
52, 63, 122, 123, 131, 145, 147, 165. MS m/z (% relative
intensity): 177 (25), 149 (11), 106 (100), 78 (56), 63 (25).
Exact mass MS calcd.: 177.0538, found: 177.0541.
+
with periodic Ar sputtering to remove impurities from the
bulk of the Pt. This was followed by a final annealing at
Methyl diazo(4-pyridyl)acetate (4-PDE)
1
273 K for 3 h. The crystals were also cleaned prior to
The synthesis of methyl diazo(4-pyridyl)acetate was
accomplished using the method described above for the syn-
thesis of methyl diazo(3-pyridyl)acetate, except that 4-acetyl
pyridine was used as the starting material. Methyl diazo(4-
pyridyl)acetate was isolated as a yellow powder. Mp 84–
+
each experiment. The cleaning procedure consisted of Ar
–
2
–5
sputtering (3 KeV, 6 mA cm at an Ar pressure of 1 Â 10
–6
torr) at 298–1073 K, followed by annealing in 1 Â 10
O
2
at 1273 K for up to 30 min. A final annealing at 1373 K
for up to 20 min was also performed. The cleanliness of the
crystal was checked with LEED and Auger electron spectro-
scopy (AES). The crystal was determined to be clean and
85 8C. UV–vis (MeCN) lmax, nm (3, L mol– cm ): 280
1
–1
–1
(14100), 250 (14300), 215 (13000). IR (CCl ) n (cm ):
3062, 3030, 2956, 2846, 2097 (C=N=N), 1719 (C=O),
4
Published by NRC Research Press

Pitters et al.
119
1
1
3
1
1
1
1
593, 1545, 1494, 1438, 1419, 1358, 1258, 1224, 1194,
Fig. 1. IR spectra of 4-PDE. (a) Solution transmission IR spectrum
1
–1
158, 1048, 990. H NMR (200 MHz, CDCl ) d (ppm):
of 4-PDE in CCl4 at 298 K, 4 cm , scaled to fit. (b) RAIR spec-
3
–
1
.88 (s, 3H), 7.40 (dd, 4.7, 1.7 Hz, 2H), 8.52 (dd, 4.7,
trum of 4-PDE monolayer on Pt(110) at 298 K, 8 cm . (c) RAIR
.7 Hz, 2H). 13C NMR (50 MHz, CDCl ) d (ppm): 52, 64,
–1
spectrum of 4-PDE monolayer after photolysis, 8 cm . Inset at top
3
–
1
17, 136, 150, 164. MS m/z (% relative intensity): 177 (31),
49 (10), 106 (100), 78 (54), 63 (21). Exact mass MS calcd.:
77.0538, found: 177.0541.
shows an expansion of the region between 2200 and 2000 cm
–
1
illustrating loss of C=N=N asymmetric stretch at 2098 cm and
–
1
growth of C=C=O stretch at 2124 cm .
Results and discussion
Saturated monolayers of analytically pure 3- and 4-PDE
on Pt were formed through a sublimation process in a UHV
chamber. In this method, the diazoester is introduced from
the gas phase where it condenses onto a cooled and cleaned
single-crystal Pt(110) or Pt(111) surface at 223 K using a
technique we have previously described.3 The multilayers
resulting from the sublimation process are thermally des-
orbed by slowly warming the Pt crystal; the maximum rate
of desorption for 3- and 4-PDE was found to be ~266–
,6
269 K using TPD and mass spectroscopic (MS) detection of
the desorbed molecules. At temperatures above that of the
maximum rate of desorption, only molecules chemisorbed
on the metal are present. For subsequent experiments, dos-
ing to form the monolayer was accomplished by holding the
temperature of the cleaned Pt above the temperature for
multilayer desorption, typically 293 K, but below that for
any further reaction.
Fig. 2. IR spectra of 3-PDE. (a) Solution transmission IR spectrum
–
1
Reflection absorption infrared (RAIR) spectroscopy was
used to characterize the resulting saturated monolayers
formed using one of the two approaches presented above.
The RAIR spectra of the saturated layer of 4-PDE and 3-
PDE on Pt(110) are shown in Figs. 1 and 2, respectively.
These are presented along with solution-phase transmission
IR spectra for comparison. Key IR bands in the monolayer
spectra include the C=N=N asymmetric and symmetric
of 3-PDE in CCl4 at 298 K, 4 cm , scaled to fit. (b) RAIR spec-
–
1
trum of 3-PDE monolayer on Pt(110) at 298 K, 4 cm . (c) RAIR
–1
spectrum of 3-PDE monolayer after photolysis, 4 cm .
–
1
–1
stretches at 2098 and 1337 cm and 2093 and 1362 cm ,
for 4-PDE and 3-PDE, respectively. The corresponding C=O
–
1
stretches are at 1712 and 1710 cm , respectively. Addi-
tional modes due to the C=C and C=N of the pyridyl ring
–
1
in the range of 1570 and 1440 cm are also evident. While
there are slight intensity differences in the C=O and C=N=N
bands between the solution and monolayer spectra due to the
difference in the two experiments (transmission vs. RAIR)
there is no significant shift in the position of the IR bands
of either the diazo C=N=N or the ester C=O bands; the
asymmetric and symmetric C=N=N and C=O bands in the
solution-phase transmission spectra occur at 2091, 1361,
and 1713 cm–1 and 2097, 1358, and 1719 cm for 3- and
–1
The monolayer was shown to be saturated by co-dosing
carbon monoxide onto the monolayer formed as described
above. Any available Pt sites would be indicated by the ap-
pearance of the Pt–CO stretch;12 however, no Pt sites were
observed. The thermal stability of the saturated monolayer
was investigated by TPD experiments and by monitoring
changes in the IR spectra as the temperature of the crystal
was increased. The TPD spectra monitored several masses
that corresponded to the major fragment ions for compounds
(m/z = 106 and 78). The TPD spectra also monitored mass
28 to detect the release of nitrogen gas that evolves during
the thermal decomposition of the diazoesters. For 3-PDE,
the only detected signal was that of m/z = 28 and no other
changes were detected for the fragments from the 3-PDE pa-
4-PDE, respectively. Because of this similarity, we conclude
that these functional groups do not interact significantly with
the metal surface in the monolayer. In the region between
–
1
1
4
600 and 1400 cm , there are differences on the order of
0–60 cm–1 when one compares the corresponding bands in
the monolayer spectrum to those in the solution phase. The
modes in this region are largely associated with the pyridyl
ring. Together, the results indicate that the monolayer is
bound through the pyridyl nitrogen, and that the rings have
a mostly perpendicular orientation because of the strong
1
1
C=N and C=O bands. Similar spectra were recorded for
2
3- and 4-PDE on Pt(111) and these are provided in the Sup-
plementary data.
Published by NRC Research Press

1
20
Can. J. Chem. Vol. 89, 2011
rent molecule. The detection of mass 28 indicated that there
was a thermal decomposition of the diazo group during the
heating of the monolayer. The onset of the detection oc-
curred at 375 K and reached a maximum at 455 K. This de-
composition temperature agrees well with that measured for
similar diazoesters such as ethyl diazophenylacetate, where a
Scheme 2. Proposed surface reaction of surface-generated carbene.
1
3
half-life of 95 min at 373 K has been determined. The fact
that no fragments from the parent molecule were detected
(
m/z = 106 and 78) indicated that the diazo group decom-
poses on the surface before any desorption of the pyridyl
groups occurs. Similar results were obtained for 4-PDE
where the onset of the release of nitrogen was observed in
the TPD at 390 K with a maximum at 465 K. The similar-
ities between the thermal stability of the diazoesters as satu-
rated monolayers and that measured for similar molecules
when not bound to a surface suggest that the Pt surface
does not alter the thermal stability of the diazo group, fur-
ther indicating that this functionality is not interacting with
the surface (vide supra). Saturated monolayers are stable in-
definitely at temperatures below the temperature of onset of
loss of nitrogen. Photoreactions described below were thus per-
formed at 293 K, above the maximum rate of desorption of the
multilayer and well below the thermal decomposition tempera-
ture.
dence for the formation of the azine and alkene products
from carbene reaction by MS identification of their parent
ions (and known major fragments) upon TPD of the photo-
lyzed monolayers. The identification of the alkene and azine
molecules was established by monitoring fragments unique
to each of the alkene and azine, respectively. The fragmen-
tation pattern for the alkene include major m/z at 298, 270,
RAIR spectra measured after irradiation of the saturated
monolayers with light of wavelength 300–400 nm are shown
in Figs. 1c and 2c, respectively. Particularly diagnostic dur-
ing the photolysis in both is the loss of the asymmetric and
symmetric C=N=N absorptions and the concomitant change
in the C=O region. The loss of nitrogen occurs only during
photolysis and this can be monitored by mass spectroscopy.
In the case of 4-PDE, there is a concomitant growth of an
2
67, and 239, while the azines had major m/z at 267 and
–
1
207. The parent ion for the azine at 326 amu could not be
observed in the electron ionization mode. The fragmentation
patterns of the alkenes and azines were determined from the
absorption at 2124 cm that can be assigned to the ketene
C=C=O stretch.5,14 The ketene formed remains stable indef-
initely. The ketene is the result of the Wolff rearrangement
and its observation is surprising because it has only been ob-
served in an Ar matrix at 10 K. Under other conditions at
higher temperatures, the ketenes are reactive. On the other
hand, for 3-PDE, the ketene stretch does not form and the
major change accompanying loss of the diazo stretches is a
6
solid-state photolysis experiments. Because m/z 298 and 239
were unique for the alkene and 207 was unique for the azines,
these masses were monitored during the TPD for identifica-
tion of the molecules. Of course, other products from the car-
bene reacting through other pathways cannot be ruled out.
We attempted to trap the carbene intermediate on the sur-
face by photolyzing the 3-PDE monolayer surface in the
presence of an overlayer of known carbene traps, such as
methanol, methyl amine (X–H insertion), and benzene
(C=C insertion). In each case, the resulting RAIR spectrum
looked identical to that shown in Fig. 2c (see Supplementary
data) and suggests that even in the presence of the overlayer
of reactant, the carbene reacts similar to when generated in
the absence of the trap. The reasons for this may include
that the intramonolayer reactions are faster than the reaction
of the generated carbene with the trapping reagent or that
the reaction with the trap is hindered because the experiment
has to be done at temperatures where the reactant is in the
solid state (frozen). Details are provided in the Supplemen-
tary data.
–1
broadening and shifting of the C=O regions at 1730 cm
and 1100–1350 cm .
–
1
The IR spectral changes observed on irradiation of 3-PDE
are similar to those measured on irradiation of multilayers of
these substrates. In multilayer (and in solid-state irradiations
6
of 3- and 4-PDE), it is easy to establish that the products
observed are due to carbene reactions, either coupling to
form the alkene or reaction with another 3- or 4-PDE to
form an azine. In the multilayer and solid-state reactions,
the azine and alkene products can be identified by MS (mul-
tilayer) and NMR and IR analytical spectroscopic techniques
(
solid state). Formation of the carbene and the resulting
azine and alkene products on the saturated monolayer are
less easy to characterize. The RAIR spectrum obtained
(
Fig. 2c) has less identifiable features. The only characteris-
tic peak is a shifting and broadening of the absorption in the
Taken together, the experimental evidence suggests that
irradiation of the 3-PDE-saturated monolayer results in for-
mation of the carbene that is efficiently scavenged by neigh-
boring 3-PDE or analogous carbene to form alkene and
azine structures on the surface (Scheme 2); these structures
lead to a broadening of the C=O ester region.
–
1
C=O region at 1730 cm . A similar RAIR spectrum, with a
broadened peak in the C=O region is obtained when the 3-
PDE-saturated monolayer is heated above 373 K, the tem-
perature where thermal loss of nitrogen occurs. For both the
thermal and photochemical experiments, we obtained evi-
Published by NRC Research Press

Pitters et al.
121
The inescapable conclusion is that the difference in reac-
tivity of 3- and 4-PDE as saturated monolayers of Pt is re-
lated to the position of the photoreactive substituent on the
pyridyl ring. For 3-PDE, the initially formed carbene is pre-
sumably formed in an orientation more closely positioned
with respect to its neighbors allowing bimolecular reactions
to occur. By contrast, the 4-PDE carbene is held at an orien-
tation where the inefficient Wolff rearrangement, with the
14719978.; (f) Ulman, A. Chem. Rev. 1996, 96 (4), 1533.
doi:10.1021/cr9502357. PMID:11848802.; (g) Hamers, R. J.
Annu. Rev. Anal. Chem. 2008, 1 (1), 707. doi:10.1146/
annurev.anchem.1.031207.112916.; (h) Haensch, C.; Hoepp-
ener, S.; Schubert, U. S. Chem. Soc. Rev. 2010, 39 (6),
2
323. doi:10.1039/b920491a. PMID:20424728.
(
(
(
2) (a) Zhou, X. L.; Zhu, X.-Y.; White, J. M. Surf. Sci. Rep.
1991, 13 (3–6), 73 [and references cited therein]. doi:10.
1016/0167-5729(91)90009-M.; (b) Zhu, X.-Y. Surf. Sci.
1997, 390 (1–3), 224. doi:10.1016/S0039-6028(97)00556-6.
migration of the –OCH to form ketene, can compete be-
3
cause of the inability of intramonolayer carbene bimolecular
reactivity. Besides the remarkable chemoselectivity observed
in this study, the observation of the ketene for 4-PDE sug-
gests that for pyridyl substrates, the surface can act to isolate
molecules and allow for the characterization of reactive in-
termediates usually only seen in Ar matrixes. We are cur-
rently trying to exploit this possibility in addition to
investigating the reactivity of the ketene and carbene mono-
layers.
3) Pitters, J. L.; Griffiths, K.; Kovar, M.; Norton, P. R.; Work-
entin, M. S. Angew. Chem. Int. Ed. 2000, 39 (12), 2144.
doi:10.1002/1521-3773(20000616)39:12<2144::AID-
ANIE2144>3.0.CO;2-V.
4) (a) Kirmse, W. Eur. J. Chem. 2002, 2193; (b) Regitz, M.;
Maas, G. Diazo Compounds. Properties and Synthesis; Aca-
demic Press, Inc.: Toronto, 1986.; (c) Tomioka, H.; Okuno,
H.; Izawa, Y. J. Chem. Soc., Perkin Trans. 2 1980, (11):
1
636. doi:10.1039/p29800001636.
5) Tomioka, H.; Ichikawa, N.; Komatsu, K. J. Am. Chem. Soc.
993, 115 (19), 8621. doi:10.1021/ja00072a015.
(
(
(
1
Supplementary data
6) Pitters, J. L. Ph. D. Thesis, The University of Western On-
Supplementary data for this article (additional spectra for
-PDE and 4-PDE on Pt(111), TPD data, tables of IR
tario, 2001.
3
7) Kasza, R. V.; Shapter, J. G.; Griffiths, K.; Norton, P. R.;
Sloan, J. J. Surf. Sci. 1994, 321 (3), L239. doi:10.1016/
stretching frequencies with assignments, and details of car-
bene trapping experiments) are available on the journal
Web site (canjchem.nrc.ca).
0
039-6028(94)90181-3.
(
8) Schwenk, E.; Papa, D. J. Org. Chem. 1946, 11 (6), 798.
doi:10.1021/jo01176a023.
9) Regitz, M.; Hocker, J.; Liedhegener, A. Org. Synth. 1973, 5,
Acknowledgements
(
1
79.
10) Yamawaki, J.; Ando, T. Chem. Lett. 1979, 8 (7), 755. doi:10.
246/cl.1979.755.
11) (a) Francis, S. A.; Ellison, A. H. J. Opt. Soc. Am. 1959, 49
2), 131. doi:10.1364/JOSA.49.000131.; (b) Haq, S.; King,
The Natural Sciences and Engineering Research Council
of Canada (NSERC), the Government of Ontario (Premier’s
Research Excellence Award), Ontario Research Develop-
ment Fund, and the Canadian Foundation for Innovation
(
(
1
(
(CFI) are thanked for financial support.
D. A. J. Phys. Chem. 1996, 100 (42), 16957. doi:10.1021/
jp960814v.
References
(
12) (a) Froitzheim, H.; Hopster, H.; Ibach, H.; Lehwald, S. Appl.
Phys. (Berl.) 1977, 13, 147; (b) Robbins, J. L.; Marucchi-
Soos, E. J. Phys. Chem. 1987, 91 (8), 2026. doi:10.1021/
j100292a007.
(
1) (a) Chechik, V.; Crooks, R. M.; Stirling, C. J. M. Adv. Ma-
ter. 2000, 12 (16), 1161. doi:10.1002/1521-4095(200008)
1
2:16<1161::AID-ADMA1161>3.0.CO;2-C.; (b) Mrksich,
M. Chem. Soc. Rev. 2000, 29 (4), 267. doi:10.1039/
a705397e.; (c) Willner, I.; Willner, B. Pure Appl. Chem.
(13) Regitz, M.; Bartz, W. Chem. Ber. 1970, 103 (5), 1477.
doi:10.1002/cber.19701030519.
2
001, 73 (3), 535. doi:10.1351/pac200173030535.; (d) Sulli-
van, T. P.; Huck, W. T. S. Eur. J. Org. Chem. 2003, 2003
1), 17. doi:10.1002/1099-0690(200301)2003:1<17::AID-
(14) (a) Kuhn, A.; Plug, C.; Wentrup, C. J. Am. Chem. Soc. 2000,
122 (9), 1945. doi:10.1021/ja993859t.; (b) Acton, A. W.; Al-
len, A. D.; Antunes, L. M.; Fedorov, A. V.; Najafian, K.;
Tidwell, T. T.; Wagner, B. D. J. Am. Chem. Soc. 2002, 124
(46), 13790. doi:10.1021/ja027347h. PMID:12431108.
(
EJOC17>3.0.CO;2-H.; (e) Daniel, M. C.; Astruc, D. Chem.
Rev. 2004, 104 (1), 293. doi:10.1021/cr030698+. PMID:
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