Precious-metal free photocatalytic production of an NADH analogue using cobalt diimine-dioxime catalysts under both aqueous and organic conditions

Article abstract of DOI:10.1039/d0cc02604b

The photocatalytic generation of an NADH synthetic analogue, i.e. 1-benzyl-1,4-dihydronicotinamide (1,4-BNAH), has been studied using the cobalt diimino-dioxime complexes and the BF2-bridged derivative as catalysts. 1,4-BNAH was produced in both aqueous a

Full text of DOI:10.1039/d0cc02604b

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DOI: 10.1039/D0CC02604B.
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DOI: 10.1039/D0CC02604B
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Precious-metal free Photocatalytic Production of a NADH
Analogue using Cobalt Diimine-dioxime Catalysts in both Aqueous
and Organic Conditions
Received 00th January 20xx,
Accepted 00th January 20xx
a
b
a
b
c
Chun-Leung Kwok, Shun-Cheung Cheng, Pui-Yu Ho, Shek-Man Yiu, Wai-Lun Man, Vonika Ka-
a
a
,a
,b
,d,e
DOI: 10.1039/x0xx00000x
Man Au, Po-Keung Tsang, Chi-Fai Leung,* Chi-Chiu Ko,* and Marc Robert*
The photocatalytic generation of a NADH synthetic analogue, i.e. 1- under aqueous conditions,17 from the corresponding conjugate
benzyl-1,4-dihydronicotinamide (1,4-BNAH) has been studied using cations, have been reported using the cobaloxime catalyst
cobalt diimino-dioxime complexes and the BF -bridged derivative [Co(dmgH) (py)Cl].
2 2
as catalysts. 1,4-BNAH was produced in both aqueous and organic
media at unprecedented turnover numbers with metal and organic
photosensitizers respectively.
Since cobalt (III) hydride species has been suggested as key
intermediates in the proton reduction catalysed by cobaloximes
1
8-21
and cobalt diimine-dioximes,
we were interested to
As the mostly widely used reductants in industrial processes,
dihydrogen and metal hydrides are currently produced by
investigate if these complexes could similarly catalyse the
reductive generation of organohydride from the corresponding
conjugate cation by the transfer of a hydride. To allow for a
better understanding of the catalytic process in diverse reaction
conditions, we studied the photocatalytic generation of a NADH
synthetic analogue, namely 1-benzyl-1,4-dihydronicotinamide
1
-2
energy-demanding reactions.
In biochemical reactions
mediated by oxidoreductase, e.g. the dark reaction of carbon
dioxide fixation,3
,4,5
organohydrides such as nicotinamide
adenine dinucleotide or its phosphorylated analogue NAD(P)H
are used, instead, for the storage and transfer of reducing
equivalents driving these reactions. Organohydrides are
important in modern chemical industry for performing
(
1,4-BNAH), from its conjugate cation, 1-benzylnicotinamide
+
triflate
(BNA ),
by
] (1 and 2; X = Cl and Br) and the BF
derivative [Co((DO) BF )pnBr ] (3) in acetonitrile and in aqueous
solutions (Schemes 1). In these photocatalytic systems,
the
cobalt
diimino-dioximes
[
Co(DO)(DOH)pnX
2
2
-bridged
chemoselective and enantiospecific biotransformation at
2
2
2
preparative scale4
,5
as well as in enzyme-catalysed
6
,7
photoelectrochemical conversion of H
2
O and CO
2
to fuels.
2+
2+
[
Ru(bpy)
3
] (RuPS ), 4,8,12-tri-n-butyl-4,8,12-triazatriangulen-
Regiospecific regeneration of the cofactors NAD(P)H from
+
ium hexafluorophosphate (TATA ) or Xanthene-type dyes, i.e.
+
NAD(P) were extensively studied under chemical, electro- and
2-
2-
Rose Bengal (RB ) and Eosin Y (EY ) can be used as
photocatalytic conditions using precious-metal catalysts,
2
+
2
particularly [Cp*Rh(bpy)(H O)] (bpy = 2,2-bipyridyl and their
8
-13
substituted derivatives) and more recently [Cp*Ir(L)(X)] (L =
-(1H-pyrazol-1-yl)benzoic acid or picolinamidate and X = H
4
2
O
-
14,15
or Cl ).
On the other hand, the regeneration of
organohydrides using earth-abundant 3d metal catalysts are
highly desirable, but far less common. The catalytic generation
of
the
NADH
synthetic
analogue
1-benzyl-1,4-
dihydronicotinamide (1,4-BNAH) by hydrogenation16 in
methanol and more recently the photogeneration of NADH
a. Department of Science and Environmental Studies, The Education University of
Hong Kong, 10 Lo Ping Road, Tai Po, N. T., Hong Kong, China.
b.
Department of Chemistry, City University of Hong Kong, Tat Chee Avenue,
Kowloon, Hong Kong, China.
Department of Chemistry, Hong Kong Baptist University, Waterloo Road,
c.
Kowloon, Hong Kong.
Université de Paris, Laboratoire d’Electrochimie Moléculaire, CNRS, F-75006 Paris,
d.
France
e.
Institut Universitaire de France (IUF), F-75005 Paris, France.
†
Footnotes relating to the title and/or authors should appear here.
Scheme 1 Structures of cobalt diimine-dioxime catalysts and photosentizers.
Electronic Supplementary Information (ESI) available: [details of any supplementary
information available should be included here]. See DOI: 10.1039/x0xx00000x
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COMMUNICATION
Journal Name
photosensitizers (PS), while triethanolamine (TEOA) was used
View Article Online
DOI: 10.1039/D0CC02604B
as a sacrificial electron donor. The light-driven (> 420 nm)
+
generation of 1,4-BNAH from BNA was performed using an
argon-purged acetonitrile or aqueous solution (5 mL) containing
various amounts of the catalyst (0.01 – 0.1 mM) and the PS (0.1
–
0.5 mM), as well as 15% triethanolamine (v/v) and BNAOTf (4
mM) in a 10 mL glass test tube sealed with a serrated rubber
septum. The product yield was determined at regular intervals
(1 hr) by HPLC-UV/Vis (95% confidence interval = 0.3 – 0.6 mol)
and photoluminescence.
2
+
In the presence of 0.25 mM RuPS , 1,4-BNAH was produced
using 1 – 3 as catalysts (0.1 mM) upon irradiation. The time
chase for yielding 1,4-BNAH of all three catalysts exhibited a
similar sigmoidal profile, which leveled off at a maximum
turnover (TON, vs catalyst) of approx. 22.1 – 23.3 (yield = 11.1 – Figure 1 Photocatalytic generation of 1,4-BNAH in acetonitrile (5 mL) containing the
+
catalyst 1 – 3 (0.1mM), BNA (4 mM) and 15%(v/v) TEOA in the presence of 0.25 mM
1
1.7 μmol) after 3 hours (Figure 1). Cumulated yields of 1,4-
RuPS2+ or TATA as photosensitizer.
+
BNAH was found to slightly decrease afterward, suggesting the
2
+
+
reductive quenching of the excited state of RuPS by large reductive quenching of the triplet state TATA * by 1,4-BNAH at
concentrations of 1,4-BNAH, which was indeed reported to be higher concentrations. Both the yield and TON were found to
2
2
an efficient sacrificial electron donor; it was also supported by increase at higher [1] (0.01 – 0.1 mM), but were less sensitive to
2
+
+
the decreasing product yield at [RuPS ] > 1 mM (Figure S1). increasing [TATA ] (0.1 – 0.5 mM) (Table 1 and Figure S4). When
+
Negligible amount of the product was obtained in the absence [TATA ] was > 0.5 mM, both product yield and TON decreased.
of catalysts. The production of 1,4-BNAH by 1 was also The generation of 1,4-BNAH at a comparable yield (11.8 μmol)
+
confirmed by its characteristic photoluminescence with em
=
and TON (23.6) using 1/TEOA/TATA in acetonitrile was
4
36 nm (ex = 348 nm) and an intensity suggesting a similar yield confirmed by the characteristic photoluminescence at em = 436
of 10.6 μmol and TON of 21.3 under the same condition (Figure nm (Trial 6, Table S1 and Figure S5). The production of 1,4-
1
S2 and Trial 5, Table S1). The reaction was then studied at BNAH was also revealed by H NMR spectroscopy for a reaction
various concentrations of 1 (0.01 – 0.1 mM) in the presence of mixture using CD
0
1
3
CN as the solvent (Figure S6). In terms of
.1 mM RuPS2+ (Figure S1 and Table 1). An increased yield of activity and energy consumption, all these photocatalytic
,4-BNAH (1.4 – 9.4 μmol) was obtained for larger [1], but the systems are more efficient when compared to reported system
TON was found to decrease slightly. The product yield was less using cobaloxime catalyst [Co(dmgH)
2
(py)Cl], which generate
2
+
+
sensitive to the change in [RuPS ] with a maximum TON of 31 1,4-BNAH (TON = 4.8 – 14) via the hydrogenation of BNA under
2
+
16
(
[1] = 25 μM) as [RuPS ] increased from 0.1 to 0.5 mM.
2
a H atmosphere at pressure from 19.4 to 77.4 atm.
To further confirm that 1,4-BNAH was obtained, the
photoreaction was performed in deuterated acetonitrile
Unexpectedly, when the above reaction was performed
1
2+
(CD
3
CN) and H NMR spectrum of the reaction mixture was using RuPS in unbuffered aqueous solution, no 1,4-BNAH was
+
performed after 6 hours of irradiation (Figure S3). The obtained. As TATA is barely soluble in water, the
production of 1,4-BNAH was demonstrated by the characteristic photogeneration of 1,4-BNAH by 1 – 3 was studied in aqueous
2
-
doublet of doublet (dd) signal at δ = 3.05 – 3.07 ppm for the environment using respectively Rose Bengal (RB ) and Eosin Y
1
6
2-
methylene protons (CH
2
) at the 4-position of 1,4-BNAH. To (EY ). Xanthene dyes were used as PS in the catalytic NADH
-
+
13
2-
verify the source of proton required for the (2e /H ) reductive regeneration by [Rh(bpy)(Cp*)] and EY was used in the
1
7
formation of the organohydride from its conjugate cation, the corresponding reaction catalyzed by [Co(dmgH)
2
(py)Cl]. In the
2
-
reaction was also performed in CD
3
CN containing 5% (v/v) D
2
O
presence of 0.25 mM RB and 15% (v/v) TEOA, 1,4-BNAH was
1
under the same condition. Subsequent H NMR analysis showed produced in unbuffered water by using respectively 1 – 3 (100
that the characteristic dd signal at δ = 3.05 – 3.07 ppm reduced μM) as the catalyst. The product yield increased with time and
+
to a large extent, suggesting that water mainly provides the H
needed in the reaction.
leveled off with maximum in the range of 2.9 – 3.3 μmol (TON =
5.7 – 6.6) after 4 hours (Figure 2 and Table 1), which decreased
Photocatalysis was performed using 1 – 3 (0.1 mM) in slightly upon further irradiation. The photocatalysis was then
2
+
precious metal-free conditions, by replacing RuPS with 0.25 performed at various [1] (10 – 100 μM). Upon increasing [1], the
mM tris(n-butyl)-triazatriangulenium hexafluorophosphate yield for 1,4-BNAH increased, while the TON decreased (Figure
+
2+
2-
(
TATA ). In contrast to the trend observed with RuPS , the yield S7a). The values were less sensitive to the change of [RB ] (0.1
of 1,4-BNAH was found to increase at a faster rate in the first – 0.25 mM) with a maximum TON of 14.8 at [1] = 10 μM and
2
-
2-
hour. A TON of 16.8 – 20 (yield = 8.4 – 10 μmol) was recorded [RB ] = 0.1 mM, while both decreased at [RB ] > 0.25 mM
2
-
after 2 hours (Figure 1). A gradual decrease in the yield was (Figure S7b). When EY was used as the PS, 1,4-BNAH was also
observed afterward, probably as a result of the more efficient produced with 1 – 3 as catalysts (Table 1). During the first 4
hours of reaction, the yield of 1,4-BNAH increased at a rate
2
| J. Name., 2012, 00, 1-3
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DOI: 10.1039/D0CC02604B
Table 1 Photocatalytic reductive generation of 1,4-BNAH in acetonitrile under varied concentrations of catalyst (cat) and photosensitizer (PS).
Yielda,b / μmol (TON)
RuPS2+
TATA+
RB+
EY+
Catalyst
[PS]/mM
cat]/ μM
0
.50
0.25
0.10
0.25
0.10
0.25
0.10
0.25
[
1
0
5
0
1.2
24.5)
3.9
(31.1)
6.4
1.2
(23.2)
3.4
(27.2)
5.9
1.4
(27.8)
3.4
(27.5)
5.7
0.4
(4.8)
1.7
(13.9)
4.6
0.5
(9.1)
1.5
(12.2)
4.3
0.5
(9.2)
1.2
(9.8)
2.0
0.7
(14.8)
1.4
(11.4)
2.4
0.4
(8.3)
1.0
(7.8)
2.3
(
2
5
1
(
25.6)
11.1
(23.6)
11.5
(23.0)
11.7
(22.6)
9.4
(18.7)
(18.3)
10.0
(19.9)
8.4
(16.8)
8.6
(17.3)
7.1
(14.3)
(8.1)
3.3
(6.6)
3.4
(6.7)
3.3
(6.7)
(9.4)
2.9
(5.8)
(9.0)
3.1
(6.2)
3.1
(6.1)
3.0
(6.1)
1
00
(22.1)
2
3
100
100








(23.3)
11.1
(22.1)
(17.2)
a
b
data corrected from the control experiments without the catalysts. confidence interval (95%) = ±0.3 mol ([cat] = 10 – 25 M) and ±0.6 mol ([cat] = 50 – 100 M).
+
Although the phosphorescence of TATA is hardly detected,
+
the long-lived triplet excited state (TATA *) with lifetime of  72

s can be characterized by the transient absorption
2
3,24
spectroscopy (Figure S10).
After adding TEOA, the lifetime
of the triplet transient absorption is shortened and new
absorption bands (at 330 and 410 nm) with much longer
lifetime were observed, indicating the formation of the reduced
+
•
species of TATA , which is denoted TATA (Figure S10). Similar
absorption features of the reduced species of tris-
+
ethoxyethanol-substituted TATA has previously been reported
2
3
in reductive quenching study with ascorbic acid. In contrast,
the addition of Co catalyst 1 only shortens the triplet absorption
lifetime without evolution of long-lived absorption bands of the
reduced species in the 300 – 800 nm region. From the lifetimes
+
of the triplet absorption of the TATA in the presence of
different concentration of 1 and TEOA, the bimolecular
+
+
Figure 2 Photocatalytic regeneration of 1,4-BNAH from BNA (4 mM) in aqueous solution
quenching rate constants (k
) of the triplet species of TATA
q
2
-
(
pH 10.97) by using 1 – 3 (100 μM), in the presence of TEOA (15% v/v) and 0.25 mM RB
9
7
-1
with 1 and TEOA were found to be 3.73  10 and 1.48  10 M
2
-
or EY .
-1
s , respectively (Figures S11 and S12). Given the bimolecular
quenching rate constant for TEOA is much lower than that of 1
2
-
slower than that with RB , but the accumulated product yield
3.1 μmol) and TON (6.2) were similar after 6 hours of
(
(by 2 orders of magnitude) and the concentration of TEOA is in
irradiation. On lowering [1] (100 – 10 μM), the 1,4-BNAH yield
was found to decrease (Figure S8). The generation of 1,4-BNAH
using 1/TEOA/RB2- or EY in water were also studied by
photoluminescence measurement and the observed yields (8.1
and 6.0 μmol respectively) and TON (16.3 and 12.0) are
comparable to the values determined by HPLC (Trials 11 and 13,
Table S1 and Figure S9). The activities of the Co diimine-dioxime
catalysts in this study illustrate their potential as candidates for
being efficient catalysts for photochemical NADH regeneration,
large excess in the photocatalytic experiment, it is not evident
to conclude on the predominant quenching pathway. To
elucidate whether the excited state of TATA is quenched by
2-
+
TEOA or 1 during photocatalysis, TA measurement were done in
+
the solution mixture of TATA containing both TEOA and 1. The
observation of a long-lived transient absorption band at 410
•
nm, identical to that of TATA and with an intensity similar to
+
the transient absorption experiment of TATA in the presence
of TEOA (Figure S10), is suggestive of the formation of the
1
7
as the recently reported cobaloximes. The generation of the
•
TATA and a predominant reductive quenching pathway under
1
active 1,4-BNAH is well demonstrated by H NMR as in previous
8
-1 -1
q
the photocatalytic conditions. The k (2.10  10 M s ) for 1,4-
reports,1
7,22
however a comparison with the activity obtained
BNAH is also determined to be larger than that for TEOA by one
upon coupling with common oxidoreductase is impossible, as
the photocatalytic conditions (acetonitrile and pH 11 aqueous
medium) are not compatible with enzymatic catalysis (buffered
neutral condition).1
order of magnitude (Figure S13). This explains for the decline of
1
,4-BNAH yield on prolonged irradiation.
The bimolecular quenching rate constants of the triplet
0-13,17
2-
species of RB in deoxygenated water were also determined
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COMMUNICATION
using laser flash photolysis (Figures S14 – 16). The quenching
Journal Name
Acknowledgement
View Article Online
DOI: 10.1039/D0CC02604B
The project is financially supported by the HK Research Grants
Council (project number 18300715 and 18301418). Financial
support (SGF-23) from EdUHK is also acknowledged.
2
-
8
rate constant of the triplet excited state of RB (k
M s ) for catalyst 1 is lower than that of TATA (by a factor 7),
q
= 5.55  10
-1
-1
+
7
-1 -1
while the quenching rate (k
q
= 3.27  10 M s ) for TEOA is two
+
times higher than in the case of TATA and is larger than the
reported rate constant measured in methanol by one order of
magnitude.25 Therefore, it is expected that the reductive
Conflicts of interest
3
2-
quenching of RB also predominates under the photocatalytic
8
-1 -1
2-
The authors declare there is not conflict of interest.
condition. Similarly, the k
q
(2.40  10 M s ) of RB for 1,4-
+
BNAH is similar to that of TATA . The larger k
q
of 1,4-BNAH with
all the photosensitizers than that of TEOA in both acetonitrile
and water suggest that competing reductive quenching with
Notes and references
1
J. D. Holladay, J. Hu, D. L. King and Y. Wang, Catal. Today,
009, 139, 244–260.
P. Rittmeyer and U. Wietelmann, Hydrides; Ullmann’s
Encyclopedia of Industrial Chemistry, 2012, Wiley-VCH,
Weinheim.
A. Wingler, P. J. Lea, W. P. Quick and R. C. Leegood, Philos.
Trans. R. Soc., B, 2000, 355, 1517–1529.
1
,4-BNAH cannot be excluded especially when their
concentration is high. This may well explain the lowered yield of
,4-BNAH in all cases upon prolonged photoreaction. On basis
of the above photochemical studies, it is proposed the PS* is
2
2
1
•-
initially formed upon photoexcitation and reduced to PS by
TEOA. The catalyst in its Co state are subsequently reduced to
CoI by the photogenerated PS•-. As hydride transfer
3
III
4
5
R. N. Patel, ACS Catal., 2011, 1, 1056–1074.
M. Hall and A. S. Bommarius, Chem. Rev., 2011, 111, 4088–
mechanisms are well reported for Rh catalysts for the reduction
4
110.
+
8,9,11,12
of NAD(P) to NAD(P)H,
it is suggested the protonation of
6
M. Hambourger, M. Gervaldo, D. Svedruzic, P. W. King, D.
Gust, M. Ghirardi, A. L. Moore and T. A. Moore, J. Am. Chem.
Soc., 2008, 130, 2015–2022.
I
III
the Co state by H
reduces the BNA to yield 1,4-BNAH by hydride transfer. The
above-proposed pathway, which is commonly observed in the
2
O then results in a Co (H) species which
+
7
8
9
1
1
S. Y. Lee, S. Y. Lim, D. Seo , J.-Y. Lee and T. D. Chung, Adv.
Energy Mater., 2016, 6, 1502207.
R. Ruppert, S. Herrmann and E. Steckhan, J. Chem. Soc., Chem.
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competing cobalt-catalyzed proton reduction process in related
catalysts,1 is also reflected by the enhanced H
8-21
production in
2
the control experiments (Trials 2, 4, 6 and 8, Table S2) without
E. Steckhan, S. Herrmann, R. Ruppert, E. Dietz, M. Frede and
E. Spika, Organometallics, 1991, 10, 1568–1577.
0 J. Ryu, S. H. Lee, D. H. Nam and C. B. Park, Adv. Mater., 2011,
+
BNA in both acetonitrile (16.8 – 18.9 mol) and water (0.8 – 2.1

mol), whereas negligible amount (0 – 0.58 and 0 mol
2
3, 1883–1888.
+
respectively) of H
consistency with the proposed PS*, PS• and Co which are
2
were produced when BNA was added. In
1 D. Westerhausen, S. Herrmann, W. Hummel and E. Steckhan,
-
I
Angew. Chem., Int. Ed. Engl., 1992, 31, 1529–1531.
susceptible to oxidative quenching, significantly lower 1,4- 12 F. Hollmann, A. Schmid and E. Steckhan, Angew. Chem., Int.
Ed., 2001, 40, 169–171.
BNAH yields were obtained in reactions performed in air (Trials
and 12, Table S1).
1
1
3 S. H. Lee, D. H. Nam and C. B. Park, Adv. Synth. Catal., 2009,
7
3
51, 2589–2594.
4 Y. Maenaka, T. Suenobu and S. Fukuzumi, J. Am. Chem. Soc.,
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6 T. Okamoto, S. Yamamoto and S. Oka, J. Mol. Catal., 1987, 39,
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The regeneration of NAD(P)H is an important process in
2
complexes bearing diimine-dioxime ligand (1 and 2) and their
BF -bridged derivative (3) are active photocatalysts for the
7
2
1
1
1
1
2
reductive generation of the NAD(P)H synthetic analogue 1,4-
2
+
BNAH from BNA in both acetonitrile and water, in the presence
7 J. A. Kim, S. Kim, J. Lee, J.-O. Baeg and J. Kim, Inorg. Chem.,
2012, 51, 8057−8063.
of metal or organic photosensitizers and TEOA as sacrificial
donor. By using 1 as the catalyst, BNAH was produced in
acetonitrile with optimized TONs of 31.1 and 19.9 respectively
8 X. Hu, B. S. Brunschwig and J. C. Peters, J. Am. Chem. Soc.,
2
007, 129, 8988−8998.
9 M. Razavet, V. Artero and M. Fontecave, Inorg. Chem., 2005,
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2
+
+
with RuPS or TATA as the photosensitizer, whereas maximum
4
TONs of 14.8 and 9.0 were recorded respectively in water, when
0 C. Baffert, V. Artero and M. Fontecave, Inorg. Chem. 2007, 46,
1817−1824.
2
-
2-
RB and EY were used instead. Product formation was
1
21 P.-A. Jacques, V. Artero, J. Pécaut and M. Fontecave, Proc.
Natl. Acad. Sci. U.S.A., 2009, 106, 20627–20632.
confirmed by chromatographic, photoluminescence and H
NMR measurements. H NMR experiment with D
1
2
O also shows
2
2 H. C. Lo, O. Buriez, J, B. Berr. And R. H. Fisher, Angew. Chem.
Int. Ed., 1999, 38, 1429–1431.
+
+
that the H required for the reduction of BNA to BNAH
originates from water. In comparison with the cobaloxime
catalysts reported earlier, the diimine-dioxime catalysts in the
current study show better activity and energy efficiency for 1,4-
BNAH regeneration. The corresponding photocatalytic
regeneration of NADH is being studied currently and the results
will be published in due course.
2
3 R. Gueret, L. Poulard, M. Oshinowo, J. Chauvin, M. Dahmane,
G. Dupeyre, P. P. Lainé, J. Fortage and M. Collomb, ACS Catal.,
2
018, 8, 3792–3802.
2
2
4 A. Shivalingam, M. A. Izquierdo, A. Le Marois, A. Vyšniauskas,
K. Suhling, M. K. Kuimova and R. Vilar, Nat. Commun., 2015, 6,
8
178–8188.
5 K. Tahara and Y. Hisaeda, Green Chem., 2011, 13, 558–561.
4
| J. Name., 2012, 00, 1-3
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DOI: 10.1039/D0CC02604B
Light-driven regeneration of a NADH analogue has been achieved using cobalt catalysts
under precious-metal free conditions in acetonitrile and water.