Meso-Phenyl-triazole bridged porphyrin-coumarin dyads: Synthesis, characterization and photophysical properties

Article abstract of DOI:10.1016/j.dyepig.2015.05.027

Novel zinc (II) meso-phenyl-triazole bridged porphyrin-coumarin dyads have been synthesized in good to excellent yields through copper (I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction of zinc (II) 5-(4-azidophenyl)-10,15,20-triphenylporphyrin with

Full text of DOI:10.1016/j.dyepig.2015.05.027

Accepted Manuscript
meso-Phenyl-triazole bridged porphyrin-coumarin dyads: Synthesis, characterization
and photophysical properties
Dileep Kumar Singh, Mahendra Nath
PII:
S0143-7208(15)00206-5
10.1016/j.dyepig.2015.05.027
DYPI 4790
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 20 February 2015
Revised Date: 14 April 2015
Accepted Date: 22 May 2015
Please cite this article as: Singh DK, Nath M, meso-Phenyl-triazole bridged porphyrin-coumarin dyads:
Synthesis, characterization and photophysical properties, Dyes and Pigments (2015), doi: 10.1016/
j.dyepig.2015.05.027.
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ACCEPTED MANUSCRIPT
Graphical Abstract
meso-Phenyl-triazole bridged porphyrin-coumarin dyads: Synthesis,
characterization and photophysical properties
*
Dileep Kumar Singh and Mahendra Nath
N
N
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O
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M
N
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M = Zn, Ni
M = Zn, Ni
M = Zn, Ni

ACCEPTED MANUSCRIPT
meso-Phenyl-triazole bridged porphyrin-coumarin dyads: Synthesis,
characterization and photophysical properties
*
Dileep Kumar Singh and Mahendra Nath
Department of Chemistry, University of Delhi, Delhi 110 007, India
Abstract: Novel zinc (II) meso-phenyl-triazole bridged porphyrin-coumarin dyads have
been synthesized in good to excellent yields through copper (I)-catalyzed Huisgen 1,3-dipolar
cycloaddition reaction of zinc (II) 5-(4-azidophenyl)-10,15,20-triphenylporphyrin with
diverse coumarinoalkynes in dimethylformamide containing ascorbic acid at 80°C. These
compounds successfully underwent demetallation in the presence of concentrated
hydrochloric acid to afford the corresponding free-base porphyrins which on treatment with
nickel acetate in chloroform-acetic acid mixture produced various nickel (II) meso-triazole
bridged porphyrin-coumarin dyads in good yields. All the newly synthesized products were
characterized on the basis of spectral data and elemental analyses. The preliminary
photophysical results revealed a significant intramolecular energy transfer between porphyrin
core and coumarin moiety in the case of zinc porphyrin analogues.
Keywords: Click chemistry, coumarin, energy-transfer, fluorescence, porphyrin, synthesis.
*
Corresponding author: Mahendra Nath
Fax: 091-11-27666605
Phone: 091-11-27667794 Extn. 186
E-mail address: mnath@chemistry.du.ac.in
1

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1
. Introduction
Porphyrins are a versatile class of π-conjugated macrocycles which display high
absorbance in visible region and possess interesting biological, photophysical and
electrochemical properties. They are highly desirable for numerous applications in diverse
fields including catalysis [1, 2], Optical limiters [3, 4], photochemistry [5, 6], medicinal
chemistry [7], anion recognition [8, 9] and material science [10-13]. In the last several
decades, the porphyrin chemistry has been explored to develop a series of novel macrocyclic
compounds through peripheral functionalization of meso-tetraarylporphyrins. Recently, the
copper (I)-catalyzed Huisgen 1,3-dipolar cycloaddition [14,15] of an azide with terminal
alkyne has become a straightforward route to afford [1,2,3]-triazole as a chemical linker to
connect porphyrins with various scaffolds such as fullerene [16-18], ferrocene [19] and
carbohydrate [20] in a single molecular framework for the study of their photophysical and
therapeutic properties. In addition, 1,2,3-triazole subunit is also found useful in the synthesis
of meso-meso-linked porphyrin dimers [21] and carbon nanotube functionalized porphyrin
analogues [22].
Among the biologically active chromophores, the coumarins are an important class of
heterocyclic compounds with diverse pharmacological and optical properties. These
molecules have been widely used as fluorescent brightening agents [23], organic light
emitting diodes [24, 25], optical sensors [26, 27], light harvesting materials [28, 29], non
linear optical materials [30] and fluorogenic probe in biological imaging [31, 32]. In the past,
various meso-substituted porphyrin-coumarin dyads [33] and different porphyrin-cored
dendrimers linked with non-conjugated coumarins as dendrons [34] have been synthesized
and investigated for their photophysical properties. The photophysical investigations revealed
that the intramolecular energy transfer occurs from coumarin moiety to the porphyrin core.
2

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Hania et al. have synthesized coumarin-porphyrin donor-acceptor systems [35] and studied
their optical properties using time- and frequency-resolved fluorescence spectroscopy. These
molecules have shown interesting photophysical characteristics and considered as a first
generation dendrimers with four donor groups for every acceptor unit. By considering the
biological significance of porphyrin, 1,2,3-triazole and coumarin scaffolds and in
continuation of our work on meso-substituted porphyrins [36-39], we report herein the
synthesis, spectroscopic characterization and photophysical properties of a novel series of
meso-phenyl-triazole bridged porphyrin-coumarin dyads.
2
. Experimental Section:
2
.1 Reagents and solvents
All the reagents and solvents used in the present work were purchased from Sigma-
Aldrich Chemical Pvt. Ltd., Bangalore, India and Merck Specialities Pvt. Ltd., Mumbai, India
and used as received unless otherwise stated. Spectroscopic grade DMF was used to measure
UV-Vis absorption and emission spectra of the samples. All the reaction involving triazole
formation was carried out in dry N atmosphere. Thin-layer chromatography (TLC) was
2
performed on silica gel 60 F254 (pre-coated aluminium sheets) from Merck. The column
chromatographic purification of all the products were carried out using either activated
neutral aluminium oxide (Brokmann grade I-II, Merck) or silica gel (60-120 mesh).
2
.2. Instruments
The melting points of all newly prepared products were determined in open capillary
1
tubes on Buchi M-560 melting point apparatus and are uncorrected. H NMR (400 MHz) and
1
3
C NMR (100 MHz) spectra were recorded in CDCl or DMSO-d on Jeol ECX-400P (400
3
6
MHz) NMR spectrometer. Chemical shifts were quoted in δ scale in parts per million (ppm)
3

ACCEPTED MANUSCRIPT
1
relative to CDCl (δ = 7.26 ppm) and DMSO-d (δ = 2.50 ppm) for H NMR and CDCl (δ =
3
6
3
1
3
7
7.00 ppm), DMSO-d (δ = 39.50 ppm) for C NMR. The coupling constants were expressed
6
as (J) and reported in Hertz (Hz). Elemental analyses for all the compounds were performed
on Elementar Analysensysteme GmbH VarioEL elemental analyzer. Infrared (IR) spectra
were recorded in film or KBr on Perkin Elmer IR spectrometer and absorption maxima (υmax
)
-1
are given in cm . UV-Vis absorption and fluorescence spectra were measured by using an
Analytik Jena’s Specord 250 UV-Vis spectrophotometer and a Varian Cary Eclipse
fluorescence spectrophotometer, respectively. The mass spectra were recorded on THERMO
Finnigan LCQ Advantage max ion trap mass spectrometer and Agilent G6530 AA LC-
HRMS Q-TOF system in positive mode.
2
.3. Synthesis of 5-(4-azidophenyl)-10,15,20-triphenylporphyrin (2)
To a stirred solution of 5-(4-aminophenyl)-10,15,20-triphenylporphyrin (1; 100 mg,
0
.158 mmol) in THF (20 mL), a saturated aqueous solution of NaNO (0.158 mmol) and
2
concentrated H SO (80 ꢀL) were added at 0-5 °C. The reaction mixture was stirred at room
2
4
temperature for 30 minutes, then a saturated aqueous solution of NaN (0.174 mmol) in water
3
was added dropwise and the reaction mixture was stirred for additional 20 minutes. The
progress of the reaction was monitored by thin layer chromatography. After completion of the
reaction, 20 mL chloroform was added to the reaction mixture. The resulting solution was
washed with water (30 mL × 3 times), the organic layer was dried over anhydrous Na SO4
2
and solvent was evaporated under reduced pressure. Thus, the crude product obtained was
purified over activated neutral alumina column using 20% chloroform in hexane as eluent.
-4
-1
-1
Purple solid; yield: 91%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 419 (158.17), 516
(6.43), 550 (3.00), 593 (1.14), 648 (1.48) nm; λEm (DMF; λEx 420 nm): 651, 717 nm; IR
-1
(
KBr) υmax/cm : 3315, 3021, 2122, 2085, 1470, 1348, 1293, 1178, 1152, 965, 798, 724, 700;
4

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1
H NMR (400 MHz, CDCl ) δ: 8.87-8.83 (m, 8H, β-pyrrolic H), 8.23-8.19 (m, 8H, meso-
3
ArH), 7.80-7.73 (m, 9H, meso-ArH), 7.43 (d, J = 8.79 Hz, 2H, meso-ArH), -2.78 (s, 2H,
1
3
internal NH); C NMR (100 MHz CDCl ) δ: 142.14, 142.07, 139.82, 138.91, 135.70,
3
1
34.54, 131.17, 127.74, 126.69, 120.32, 120.25, 120.12, 118.81, 117.42; HRMS (ESI, m/z)
+
calcd for C H N : 656.2557 [M+H] ; found 656.2558.
4
4
30
7
2
.4. Synthesis of zinc (II) 5-(4-azidophenyl)-10,15,20-triphenylporphyrin (3)
To a solution of 5-(4-azidophenyl)-10,15,20-triphenylporphyrin (2; 50 mg, 0.076 mmol) in
chloroform (10 mL), a solution of zinc acetate (20 mg, 0.091 mmol) in methanol (1 mL) was
added. The reaction mixture was stirred at 25 °C for 30 minutes. After completion of the
reaction, the mixture was washed with water and CHCl layer was dried over anhydrous
3
Na SO . The solvent was evaporated under reduced pressure to afford the crude product,
2
4
which was purified by silica gel column using 30% chloroform in hexane as eluent. The pure
product was obtained as a purple solid in 93% yield. The spectroscopic data of the porphyrin
(3) were matched with the reported data [17].
2
.5. Synthesis of 7-trifluoromethylsulfonyloxycoumarins (5a-c)
The coumarins (5a-c) were synthesized by the reaction of 7-hydroxycoumarins (4a-c)
(
0.56 mmol) and trifluoromethanesulfonic anhydride (0.72 mmol) in the presence of Et N
3
(0.74 mmol) as reported in the literature [40]. The spectral data of known compounds (5a-b)
are found to be in good agreement with the reported data [41, 42] whereas the
characterization data of unknown compound 5c are given below.
2
.5.1. (6-Chloro-4-methyl-2-oxo-2H-chromen-7-yl)trifluoromethanesulfonate (5c)
-1
White solid; yield: 93%, mp 142-144 °C; IR (film) υmax/cm : 3053, 2930, 1730, 1630,
1
1
423, 1209, 1134, 1036, 896, 863; H NMR (400 MHz, CDCl ) δ: 7.74 (s, 1H, ArH), 7.36 (s,
3
5

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4
4
13
1
H, ArH), 6.38 (d, J = 1.46 Hz, 1H, CH), 2.44 (d, J = 1.46 Hz, 3H, CH ); C NMR (100
3
MHz, CDCl ) δ: 158.85, 152.20, 150.26, 146.64, 126.57, 122.92, 120.82, 116.94, 116.84,
3
+
1
3
1
12.09, 18.63; HRMS (ESI, m/z) calcd for C H ClF O S: 342.9649 [M+H] ; found
11
7
3
5
42.9637; Anal. Calcd. for C H ClF O S: C, 38.55; H, 1.76; S, 9.36. Found: C, 38.57; H,
1
1
6
3
5
.75; S, 9.32.
2.6. Synthesis of 7-trimethylsilylethynylchromen-2-ones (6a-c)
The title compounds were prepared by the Sonogashira reaction of 7-
trifluoromethylsulfonyloxycoumarins (5a-c; 0.32 mmol) with trimethylsilylacetylene (0.4
mmol) in DMF (2 mL) in the presence of bis(triphenylphosphine)palladium(II) dichloride
(0.007 mmol) and triethylamine (2.5 mmol) as reported in the literature procedure [43]. The
spectral and analytical data of known compounds (6a-b) were found in good agreement with
the reported data [41, 42]. The characterization data of compound (6c) are given below.
2.6.1. 6-Chloro-4-methyl-7-trimethylsilanylethynylchromen-2-one (6c)
-1
White solid; yield: 78%, mp 156-158 °C; IR (Film) υmax/cm : 2960, 1734, 1386, 1246,
1
1
157, 841, 759; H NMR (400 MHz, CDCl ) δ: 7.58 (s, 1H, ArH), 7.42 (s, 1H, ArH), 6.31 (s,
3
4
13
1
H, CH), 2.40 (d, J = 1.46 Hz, 3H, CH ), 0.29 (s, 9H, Si(CH ) ); C NMR (100 MHz CDCl )
3
3 3
3
δ: 159.79, 151.32, 150.73, 131.50, 125.98, 124.64, 121.42, 120.86, 116.32, 104.32, 99.76,
+
1
8.49, -0.33; ESI-MS: m/z = 291.2 (M+H) ; Anal. Calcd. for C H ClO Si: C, 61.95; H, 5.20.
15
15
2
Found: C, 62.12; H, 5.41.
2.7. Synthesis of 7-ethynylcoumarins (7a-c)
The 7-ethynylcoumarins (7a-c) were prepared from 7-trimethylsilylethynylcoumarins
(6a-c) according to the literature method [43]. The spectral data of compounds (7a-b) are
6

ACCEPTED MANUSCRIPT
matched with the reported data [41, 42] and the characterization data of unknown compound
(7c) are given below.
2.7.1. 6-Chloro-7-ethynyl-4-methyl-chromen-2-one (7c)
-1
Brown solid; yield: 81%, mp 144-146 °C; IR (Film) υmax/cm : 3235, 2960, 2110, 1718,
1
4
1
382, 1197, 1154, 1081, 902, 878, 705; H NMR (400 MHz, CDCl ) δ: 7.61 (d, J = 1.46 Hz,
3
4
4
1
H, ArH), 7.47 (d, J = 1.46 Hz, 1H, ArH), 6.33 (s, 1H, CH), 3.54 (d, J = 1.46 Hz, 1H, -
4
13
C≡CH), 2.41 (d, J = 1.46 Hz, 3H, CH ); C NMR (100 MHz, CDCl ) δ: 159.60, 151.31,
3
3
150.65, 131.52, 124.95, 124.81, 121.98, 121.29, 116.58, 85.49, 78.97, 18.49; ESI-MS: m/z =
+
2
19.2 (M+H) ; Anal. Calcd. for C H ClO : C, 65.92; H, 3.23. Found: C, 65.87 H, 3.24.
12
7
2
2.8 Synthesis of propargyloxycoumarins (8a-e)
The propargyloxycoumarins (8a-e) were synthesized from 7-hydroxycoumarins (4a-d;
.56 mmol) or 4-hydroxycoumarin (4e; 0.56 mmol) and propargylbromide (0.84 mmol) by
0
following the literature procedure and characterized on the basis of spectral data [44, 45]. The
characterization data of compounds (8c-d) are presented below.
2.8.1. 6-Chloro-4-methyl-7-prop-2-ynyloxy-chromen-2-one (8c)
-1
White solid; yield: 84%, mp 208-210 °C; IR (Film) υmax/cm : 3287, 3060, 2926, 2133,
1
1
736, 1604, 1364, 1276, 1157, 1054, 881, 845; H NMR (400 MHz, CDCl ) δ: 7.59 (s, 1H,
3
4
4
ArH), 7.05 (s, 1H, ArH), 6.20 (s, 1H, CH), 4.85 (d, J = 2.20 Hz, 2H, OCH ), 2.61 (t, J = 2.20
2
13
Hz, 1H, -C≡CH), 2.39 (s, 3H, CH ); C NMR (100 MHz, CDCl ) δ: 160.48, 155.40, 153.21,
3
3
+
1
51.49, 125.58, 119.31, 114.52, 113.30, 102.12, 57.05, 18.61; ESI-MS: m/z = 249.1 (M+H) ;
Anal. Calcd. for C H ClO : C, 62.79; H, 3.65. Found: C, 62.53; H, 3.62.
13
9
3
7

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2.8.2. 4-Chloromethyl-7-prop-2-ynyloxy-chromen-2-one (8d)
-1
White solid; yield: 79%, mp 142-144 °C; IR (Film) υmax/cm : 3242, 2926, 2127, 1720,
1
1
606, 1376, 1265, 1139, 1057, 821, 739; H NMR (400 MHz, CDCl ) δ: 7.59 (d, J = 9.52 Hz,
3
4
1
H, ArH), 6.98-6.96 (m, 2H, ArH), 6.43 (s, 1H, CH), 4.77 (d, J = 2.93 Hz, 2H, OCH ), 4.62 (s,
2
4
13
2
H, CH Cl), 2.58 (t, J = 2.93 Hz, 1H, -C≡CH); C NMR (100 MHz, CDCl + DMSO-d ) δ:
2
3
6
158.62, 158.15, 153.27, 148.86, 124.58, 110.98, 110.72, 109.35, 100.41, 77.51, 76.47, 54.44,
+
3
9.57; ESI-MS: m/z = 249.1 (M+H) ; Anal. Calcd. for C H ClO : C, 62.79; H, 3.65. Found:
13
9
3
C, 62.58; H, 3.53.
2.9. General procedure for the synthesis of zinc (II) meso-phenyl-triazole bridged porphyrin-
coumarin dyads (9a,c,e, 10a,c,e,g and 11a)
To a well stirred solution of zinc (II) 5-(4-azidophenyl)-10,15,20-triphenylporphyrin (3;
0
.139 mmol) in DMF (10 mL), CuSO .5H O (6.94 mg, 0.028 mmol), ascorbic acid (9.79 mg,
4
2
0.055 mmol) and the corresponding coumarinoalkynes (7a-c or 8a-e; 0.166 mmol) were added
and the reaction mixture was stirred at 80 °C for 2 hours under nitrogen. After completion of
the reaction, the mixture was allowed to cool at room temperature and diluted with 50 mL
chloroform. The resulting solution was washed thoroughly with water, the organic layer was
dried over anhydrous sodium sulphate and evaporated to dryness. Thus, the crude product
obtained was purified over silica gel column using 2% methanol in chloroform as eluent.
2
.9.1. Zinc (II) 4-methyl-7-{1-[4-(10,15,20-triphenylporphyrin-5-yl)-phenyl]-1H-[1,2,3]
triazol-4-yl}-chromen-2-one (9a)
Purple solid; yield: 87%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 428
-4
-1
-1
-1
(
215.53), 560 (7.17), 601 (2.99) nm; λEm (DMF; λ 420 nm): 607, 660 nm; IR (KBr) υ /cm :
Ex max
1
2
924, 2854, 1712, 1619, 1261, 1073, 1035, 796, 754, 704; H NMR (400 MHz, DMSO-d ) δ:
6
8

ACCEPTED MANUSCRIPT
9.82 (s, 1H, triazole H), 8.87 (d, J = 4.39 Hz, 2H, β-pyrrolic H), 8.82-8.78 (m, 6H, β-pyrrolic
H), 8.46 (d, J = 8.05 Hz, 2H, meso-ArH), 8.38 (d, J = 8.05 Hz, 2H, meso-ArH), 8.20-8.18 (m,
H, meso-ArH), 8.08-8.04 (m, 1H, ArH), 8.01 (s, 1H, ArH), 7.96-7.91 (m, 1H, ArH), 7.80-7.79
6
1
3
(
m, 9H, meso-ArH), 6.44 (s, 1H, CH), 2.50 (s, 3H, CH ); C NMR (100 MHz, DMSO-d ) δ:
3
6
1
1
1
59.85, 153.60, 153.11, 149.48, 149.42, 149.13, 146.16, 143.45, 142.72, 135.93, 135.48,
34.24, 133.80, 131.98, 131.79, 131.74, 131.48, 127.59, 126.70, 126.43, 121.47, 121.26,
20.72, 120.58, 119.45, 118.67, 118.38, 114.33, 112.64, 18.13; HRMS (ESI, m/z) calcd for
+
C H N O Zn: 902.2216 [M+H] ; found 902.2173. Anal. Calcd. for C H N O Zn.H O: C,
56
36
7
2
56 35
7
2
2
73.00; H, 4.05; N, 10.64. Found: C, 72.92; H, 4.15; N, 10.32.
2.9.2. Zinc (II) 7-{1-[4-(10,15,20-triphenylporphyrin-5-yl)-phenyl]-1H-[1,2,3]triazol-4-yl}-
chromen-2-one (9c)
-4
-1
-1
Purple solid; yield: 87%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 427
-
(
151.28), 560 (4.93), 601 (1.85) nm; λEm (DMF; λ 420 nm): 607, 659 nm; IR (Film) υmax/cm
Ex
1
1
:
2926, 1716, 1617, 1340, 1262, 1205, 1101, 1003, 797, 755; H NMR (400 MHz, DMSO-d ),
6
δ: 9.81 (s, 1H, triazole H), 8.87 (d, J = 5.13 Hz, 2H, β-pyrrolic H), 8.82-8.78 (m, 6H, β-pyrrolic
H), 8.46 (d, J = 8.05 Hz, 2H, meso-ArH), 8.38 (d, J = 8.79 Hz, 2H, meso-ArH), 8.20-8.18 (m,
6H, meso-ArH), 8.12 (d, J = 9.52 Hz, 1H, CH), 8.07-8.01 (m, 2H, ArH), 7.89 (s, 1H, ArH),
13
7
.80-7.79 (m, 9H, meso-ArH), 6.54 (d, J = 9.52 Hz, 1H, CH); C NMR (100 MHz, DMSO-d )
6
δ: 159.98, 154.16, 149.45, 149.38, 149.11, 146.21, 143.94, 143.43, 142.71, 135.89, 135.45,
134.21, 133.73, 131.94, 131.77, 131.72, 131.45, 129.31, 127.57, 126.66, 121.44, 121.38,
+
1
20.68, 120.55, 118.65, 118.57, 118.32, 116.11, 112.51; ESI-MS: m/z = 888.0 (M+H) ; Anal.
Calcd. for C H N O Zn.H O: C, 72.81; H, 3.89; N, 10.81. Found: C, 72.83; H, 3.92; N,
55
33
7
2
2
10.62.
9

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2.9.3. Zinc (II) 6-chloro-4-methyl-7-{1-[4-(10,15,20-triphenylporphyrin-5-yl)-phenyl]-1H-
[1,2,3]triazol-4-yl}-chromen-2-one (9e)
-4
-1
-1
Purple solid; yield: 78%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 427
-
(
169.39), 560 (5.57), 601 (2.21) nm; λEm (DMF; λ 420 nm): 607, 659 nm; IR (Film) υmax/cm
Ex
1
1
:
2921, 1714, 1613, 1339, 1262, 1173, 1066, 1001, 798, 753; H NMR (400 MHz, CDCl +
3
DMSO-d ) δ: 8.94 (s, 1H, trizole H), 8.77-8.71 (m, 8H, β-pyrrolic H), 8.30-8.23 (m, 3H, meso-
6
ArH and ArH), 8.07-8.04 (m, 8H, meso-ArH), 7.61-7.58 (m, 9H, meso-ArH), 7.28 (s, 1H,
13
ArH), 6.22 (s, 1H, CH), 2.33 (s, 3H, CH3); C NMR (100 MHz, DMSO-d + CDCl ) δ:
6
3
1
1
1
59.72, 151.62, 150.61, 149.65, 149.54, 149.52, 149.07, 144.27, 143.10, 142.82, 135.54,
35.24, 134.13, 131.72, 131.50, 131.45, 130.79, 126.91, 126.19, 126.01, 125.79, 121.97,
+
20.63, 120.44, 120.25, 118.29, 117.85, 117.18, 115.83, 18.11; ESI-MS: m/z = 936.0 (M+H) ;
Anal. Calcd. for C H ClN O Zn: C, 71.72; H, 3.65; N, 10.46. Found: C, 71.65; H, 3.55; N,
56
34
7
2
10.46.
2.9.4. Zinc (II) 4-methyl-7-{1-[4-(10,15,20-triphenylporphyrin-5-yl)-phenyl]-1H-[1,2,3]
triazol-4-ylmethoxy}-chromen-2-one (10a)
-4
-1
-1
Purple solid; yield: 80%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 427
-
(
195.50), 560 (6.46), 600 (2.72) nm; λEm (DMF; λ 420 nm): 606, 659 nm; IR (Film) υmax/cm
Ex
1
1
:
2924, 1689, 1607, 1387, 1338, 1209, 1065, 992, 797, 758, 703; H NMR (400 MHz, DMSO-
d6) δ: 9.29 (s, 1H, triazole H), 8.85 (d, J = 4.39 Hz, 2H, β-pyrrolic H), 8.82-8.79 (m, 6H, β-
pyrrolic H), 8.40 (d, J = 8.05 Hz, 2H, meso-ArH), 8.33 (d, J = 8.05 Hz, 2H, meso-ArH), 8.20-
8.18 (m, 6H, meso-ArH), 7.80-7.79 (m, 9H, meso-ArH), 7.70 (d, J = 8.05 Hz, 1H, ArH), 7.26
(
(
d, J = 2.20 Hz, 1H, ArH), 7.11 (dd, J = 8.79, J = 2.20 Hz, 1H, ArH), 6.24 (s, 1H, CH), 5.47
1
2
+
s, 2H, OCH ), 2.39 (s, 3H, CH ); ESI-MS: m/z = 932.0 (M+H) ; Anal. Calcd. for
2
3
C H N O Zn.H O: C, 71.96; H, 4.13; N, 10.31. Found: C, 72.12; H, 4.14; N, 10.23.
57
37
7
3
2
1
0

ACCEPTED MANUSCRIPT
2.9.5. Zinc (II) 7-{1-[4-(10,15,20-triphenylporphyrin-5-yl)-phenyl]-1H-[1,2,3]triazol-4-yl
methoxy}-chromen-2-one (10c)
-4
-1
-1
Purple solid; yield: 73%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 427
-
(
232.06), 560 (7.42), 600 (3.02) nm; λEm (DMF; λ 420 nm): 607, 659 nm; IR (Film) υmax/cm
Ex
1
1
:
2926, 1724, 1615, 1068, 992, 795, 750; H NMR (400 MHz, DMSO-d ) δ: 9.27 (s, 1H,
6
triazole H), 8.87-8.79 (m, 8H, β-pyrrolic H), 8.40 (d, J = 7.79 Hz, 2H, meso-ArH), 8.32 (d, J =
7
.33 Hz, 2H, meso-ArH), 8.20-8.18 (m, 6H, meso-ArH), 8.02-7.96 (m, 1H, CH), 7.79-7.78 (m,
H, meso-ArH), 7.68-7.62 (m, 1H, ArH), 7.27 (s, 1H, ArH), 7.12-7.08 (m, 1H, ArH), 6.33-6.30
9
1
3
(
m, 1H, CH), 5.47 (s, 2H, OCH ); C NMR (100 MHz, DMSO-d ) δ: 161.13, 160.36, 155.40,
2
6
1
1
1
49.48, 149.41, 149.14, 144.36, 143.45, 143.30, 142.73, 135.95, 135.38, 134.24, 131.97,
31.83, 131.78, 131.52, 129.65, 127.59, 126.70, 123.53, 120.73, 120.58, 118.72, 118.42,
+
13.04, 112.84, 112.77, 101.74, 61.75; ESI-MS: m/z = 918.0 (M+H) ; Anal. Calcd. for
C H N O Zn.1.5H O: C, 71.07; H, 4.05; N, 10.36. Found: C, 71.23; H, 3.97; N, 10.42.
56
35
7
3
2
2.9.6. Zinc (II) 6-chloro-4-methyl-7-{1-[4-(10,15,20-triphenylporphyrin-5-yl)-phenyl]-1H-
[1,2,3]triazol-4-ylmethoxy}-chromen-2-one (10e)
-4
-1
-1
Purple solid; yield: 73%; mp >300 °C; UV-Vis (DMF) λmax (ε×10 , M cm ): 427
-
(
190.64), 560 (6.10), 600 (2.36) nm; λEm (DMF; λ 420 nm): 606, 659 nm; IR (Film) υmax/cm
Ex
1
1
:
2922, 1727, 1605, 1495, 1339, 1276, 1158, 1068, 993, 797, 757; H NMR (400 MHz, CDCl3
+
DMSO-d ) δ: 8.65-8.62 (m, 8H, β-pyrrolic H), 8.39 (s, 1H, triazole H), 8.16-8.11 (m, 2H,
6
meso-ArH), 7.99-7.91 (m, 8H, meso-ArH), 7.54-7.47 (m, 9H, meso-ArH), 7.43 (s, 1H, ArH),
7
9
6
.03 (s, 1H, ArH), 5.97 (s, 1H, CH), 5.30 (s, 2H, OCH ), 2.34 (s, 3H, CH ); ESI-MS: m/z =
2 3
+
66.0 (M+H) ; Anal. Calcd. for C H ClN O Zn.H O: C, 69.45; H, 3.89; N, 9.95. Found: C,
57
36
7
3
2
9.65; H, 4.13; N, 10.12.
1
1

ACCEPTED MANUSCRIPT
2.9.7. Zinc (II) 4-chloromethyl-7-{1-[4-(10,15,20-triphenylporphyrin-5-yl)-phenyl]-1H-
[
1,2,3]triazol-4-ylmethoxy}-chromen-2-one (10g)
Purple solid; yield: 67%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 427 (190.23),
-4
-1
-1
-1
5
60 (6.28), 601 (2.39) nm; λEm (DMF; λEx 420 nm): 607, 659 nm; IR (Film) υmax/cm : 3054,
1
2
921, 1731, 1614, 1392, 1339, 1267, 1204, 1069, 1001, 993, 796, 754; H NMR (400 MHz,
DMSO-d ) δ: 9.31 (s, 1H, triazole H), 8.85 (d, J = 4.39 Hz, 2H, β-pyrrolic H), 8.81-8.78 (m, 6H,
6
β-pyrrolic H), 8.40 (d, J = 8.05 Hz, 2H, meso-ArH), 8.33 (d, J = 8.05 Hz, 2H, meso-ArH), 8.19-
8.18 (m, 6H, meso-ArH), 7.80-7.79 (m, 10H, meso-ArH and ArH), 7.32 (s, 1H, ArH), 7.19-7.17
13
(
m, 1H, ArH), 6.54 (s, 1H, CH), 5.50 (s, 2H, OCH ), 5.00 (s, 2H, CH Cl); C NMR (100 MHz,
2 2
DMSO-d ) δ: 161.29, 160.17, 155.24, 150.89, 149.55, 149.49, 149.21, 143.57, 143.49, 143.39,
6
142.77, 135.99, 135.45, 134.30, 132.02, 131.87, 131.83, 131.55, 127.66, 126.77, 126.54, 123.57,
120.80, 120.66, 118.77, 118.51, 113.03, 112.38, 110.91, 102.16, 61.83, 41.38; ESI-MS: m/z =
+
9
66.0 (M+H) ; Anal. Calcd. for C H ClN O Zn: C, 70.74; H, 3.75; N, 10.13. Found: C, 70.69;
57
33
7
3
H, 3.78; N, 10.23.
2.9.8. Zinc (II) 4-{1-[4-(10,15,20-triphenylporphyrin-5-yl)-phenyl]-1H-[1,2,3]triazol-4-yl
methoxy}-chromen-2-one (11a)
-4
-1
-1
Purple solid; yield: 83%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 427
-
(
151.10), 560 (4.88), 601 (1.66) nm; λEm (DMF; λ 420 nm): 607, 657 nm.; IR (Film) υmax/cm
Ex
1
1
:
2922, 2851, 1720, 1621, 1490, 1339, 1236, 1105, 1069, 993, 795, 750; H NMR (400 MHz,
CDCl ) δ = 8.98-8.95 (m, 6H, β-pyrrolic H), 8.90 (d, J = 4.39 Hz, 2H, β-pyrrolic H), 8.38-8.37
3
(m, 2H, meso-ArH), 8.28 (s, 1H, triazole H), 8.23-8.21 (m, 6H, meso-ArH), 8.06-8.01 (m, 2H,
meso-ArH), 7.84-7.70 (m, 9H, meso-ArH), 7.57-7.51 (m, 2H, ArH), 7.33-7.30 (m, 2H, ArH),
+
5
.83 (s, 1H, CH), 5.20 (s, 2H, OCH ); ESI-MS: m/z = 918.0 (M+H) ; Anal. Calcd. for
2
C H N O Zn.H O: C, 71.16; H, 3.98; N, 10.46. Found: C, 71.53; H, 3.83; N, 10.52.
56
35
7
3
2
1
2

ACCEPTED MANUSCRIPT
2.10. General procedure for the demetallation of zinc porphyrins (9a,c, 10a,c,e,g and 11a)
To a solution of zinc porphyrins (50 mg) in CHCl (10 mL), conc. HCl (200 ꢀL) was
3
added. The reaction mixture was stirred at 25°C for 15 minutes. After completion of the
reaction, the mixture was washed with water (50 mL × 3 times). The organic layer was dried
over anhydrous sodium sulphate and evaporated under reduced pressure. Thus, the crude
products obtained after the demetallation of zinc porphyrins (9a,c and 10a,c,e,g) were found to
be insoluble in most of organic solvents at 25°C and therefore, used as such for the synthesis of
corresponding nickel porphyrins (9b,d and 10b,d,f,h). However, the free-base porphyrin (11b)
was purified over neutral alumina column using 80% chloroform in hexane as solvent.
2.10.1. 4-{1-[4-(10,15,20-Triphenylporphyrin-5-yl)-phenyl]-1H-[1,2,3]triazol-4-ylmethoxy}-
chromen-2-one (11b)
-4
-1
-1
Dark purple solid; yield: 84%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 418
(
132.90), 516 (4.93), 548 (2.83), 595 (0.51), 647 (1.01) nm; λEm (DMF; λ 420 nm): 650, 718
Ex
-1
nm; IR (Film) υmax/cm : 3317, 2921, 2851, 1720, 1622, 1459, 1349, 1237, 1106, 966, 800, 750;
1
H NMR (400 MHz, CDCl ) δ: 8.90-8.87 (m, 6H, β-pyrrolic H), 8.81 (d, J = 4.39 Hz, 2H, β-
3
pyrrolic H), 8.37-8.33 (m, 3H, triazole H and meso-ArH), 8.23-8.21 (m, 6H, meso-ArH), 8.11-
8.07 (m, 2H, meso-ArH), 7.89 (d, J = 7.32 Hz, 1H, ArH), 7.81-7.76 (m, 9H, meso-ArH), 7.58
(t, J = 7.32 Hz, 1H, ArH), 7.36 (d, J = 8.05 Hz, 1H, ArH), 7.29 (t, J = 7.32 Hz, 1H, ArH), 5.98
1
3
(
s, 1H, CH), 5.52 (s, 2H, OCH ), -2.75 (s, 2H, internal NH); C NMR (100 MHz, CDCl ) δ:
2
3
1
1
1
4
64.92, 162.57, 153.35, 143.33, 142.35, 141.93, 136.20, 135.49, 134.51, 132.54, 131.38,
27.82, 126.73, 126.46, 123.95, 123.14, 121.74, 120.73, 120.44, 118.73, 117.57, 116.79,
+
15.39, 91.29, 62.48; ESI-MS: m/z = 856.2 (M+H) ; Anal. Calcd. for C H N O : C, 78.58; H,
56
37
7
3
.36; N, 11.45. Found: C, 78.84; H, 4.52; N, 11.24.
1
3

ACCEPTED MANUSCRIPT
2.11. General procedure for the synthesis nickel (II) meso-phenyl-triazole bridged porphyrin-
coumarin dyads (9b,d, 10b,d,f,h and 11c)
To a solution of free-base porphyrins (0.035 mmol) in CHCl (10 mL), nickel acetate
3
(0.053 mmol) in acetic acid (1 mL) was added. The reaction mixture was refluxed for 10 hours
under stirring. After completion of the reaction, the reaction mixture was cooled to 25 °C and
washed with water to remove acetic acid. The organic layer was dried over anhydrous sodium
sulphate and solvent was evaporated under reduced pressure. The crude product was purified
by column chromatography over silica gel using chloroform as eluent.
2
.11.1. Nickel (II) 4-methyl-7-{1-[4-(10,15,20-triphenylporphyrin-5-yl)-phenyl]-1H-[1,2,3]-
triazol-4-yl}-chromen-2-one (9b)
Reddish brown solid; yield: 97%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 416
-4
-1
-1
-1
(
55.10), 530 (4.17) nm; IR (Film) υmax/cm : 3107, 1699, 1617, 1520, 1351, 1226, 1075, 1002,
1
8
01, 753, 703; H NMR (400 MHz, CDCl ) δ: 8.79-8.73 (m, 8H, β-pyrrolic H), 8.49 (s, 1H,
3
triazole H), 8.20 (d, J = 8.05 Hz, 2H, meso-ArH), 8.11 (d, J = 8.42 Hz, 2H, meso-ArH), 8.02-
.80 (m, 6H, meso-ArH), 7.97 (s, 1H, ArH), 7.85 (s, 1H, ArH), 7.73-7.66 (m, 10H, meso-ArH
and ArH), 6.33 (s, 1H, CH), 2.48 (s, 3H, CH ); HRMS (ESI, m/z) calcd for C H N NiO :
7
3
56 36
7
2
+
8
1
96.2278 [M+H] ; found 896.2249; Anal. Calcd. for C H N NiO : C, 75.02; H, 3.93; N,
56 35 7 2
0.94. Found: C, 75.35; H, 3.90; N, 10.83.
.11.2. Nickel (II) 7-{1-[4-(10,15,20-triphenylporphyrin-5-yl)-phenyl]-1H-[1,2,3]triazol-4-yl}-
2
chromen-2-one (9d)
Reddish brown solid; yield: 93%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 416
-4
-1
-1
-1
(
72.14), 530 (5.28) nm; IR (Film) υmax/cm : 2923, 2851, 1710, 1617, 1353, 1235, 1075, 1004,
1
7
98, 755, 703; H NMR (400 MHz, CDCl ) δ: 8.79-8.72 (m, 8H, β-pyrrolic H), 8.47 (s, 1H,
3
1
4

ACCEPTED MANUSCRIPT
triazole H), 8.20 (d, J = 8.05 Hz, 2H, meso-ArH), 8.09 (d, J = 8.05 Hz, 2H, meso-ArH), 8.02-
8.00 (m, 6H, meso-ArH), 7.93 (d, J = 7.32 Hz, 1H, CH), 7.84 (s, 1H, ArH), 7.71-7.66 (m, 10H,
13
meso-ArH and ArH), 7.54 (d, J = 7.32 Hz, 1H, ArH), 6.43 (d, J = 8.79 Hz, 1H, CH); C NMR
(
100 MHz, CDCl ) δ: 160.58, 154.43, 146.89, 142.88, 142.85, 142.80, 142.69, 142.16, 142.04,
3
140.69, 136.30, 134.84, 133.67, 132.58, 132.42, 132.36, 131.51, 128.41, 127.82, 126.91,
121.78, 119.39, 119.25, 118.98, 118.75, 118.62, 116.73, 116.56, 113.54; ESI-MS: m/z = 882.5
+
(
M+H) ; Anal. Calcd. for C H N NiO : C, 74.85; H, 3.77; N, 11.11. Found: C, 74.65; H,
55
33
7
2
3.85; N, 11.22.
2.11.3. Nickel (II) 4-methyl-7-{1-[4-(10,15,20-triphenylporphyrin-5-yl)-phenyl]-1H-[1,2,3]-
triazol-4-ylmethoxy}-chromen-2-one (10b)
-4
-1
-1
Reddish brown solid; yield: 94%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 416
-1
(
81.93), 529 (6.15) nm; IR (Film) υmax/cm : 3056, 2919, 2850, 1726, 1613, 1353, 1071, 1006,
1
7
5
8
7
98, 753, 701; H NMR (400 MHz, CDCl ) δ: 8.79-8.76 (m, 6H, β-pyrrolic H), 8.71 (d, J =
3
.13 Hz, 2H, β-pyrrolic H), 8.28 (s, 1H, triazole H), 8.16 (d, J = 8.05 Hz, 2H, meso-ArH), 8.05-
.00 (m, 8H, meso-ArH), 7.73-7.66 (m, 9H, meso-ArH), 7.54 (d, J = 9.52 Hz, 1H, ArH), 7.03-
13
.01 (m, 2H, ArH), 6.17 (s, 1H, CH), 5.42 (s, 2H, OCH ), 2.41 (s, 3H, CH ); C NMR (100
2
3
MHz, CDCl ) δ: 161.12, 160.99, 155.11, 152.38, 144.00, 142.84, 142.79, 142.69, 142.16,
3
1
1
1
1
41.94, 140.68, 139.27, 136.36, 134.76, 133.65, 132.56, 132.41, 132.35, 131.50, 127.81,
26.89, 125.73, 121.29, 119.38, 119.24, 119.00, 116.74, 114.14, 114.05, 112.34, 102.18, 62.22,
+
8.63; ESI-MS: m/z = 926.0 (M+H) ; Anal. Calcd. for C H N NiO : C, 73.88; H, 4.02; N,
57
37
7
3
0.58. Found: C, 74.03; H, 4.22; N, 10.32.
2.11.4. Nickel (II) 7-{1-[4-(10,15,20-triphenylporphyrin-5-yl)-phenyl]-1H-[1,2,3]triazol-4-
ylmethoxy}-chromen-2-one (10d)
1
5

ACCEPTED MANUSCRIPT
-4
-1
-1
Reddish brown solid; yield: 91%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 416
-1
(
58.26), 529 (4.34) nm; IR (Film) υmax/cm : 3054, 2916, 2848, 1719, 1618, 1352, 1292, 1133,
1
1
004, 797, 749; H NMR (400 MHz, CDCl ) δ: 8.77-8.53 (m, 9H, β-pyrrolic H and triazole H),
3
8.24 (d, J = 8.05 Hz, 2H, meso-ArH), 8.08 (d, J = 8.05 Hz, 2H, meso-ArH), 8.02-7.95 (m, 6H,
meso-ArH), 7.90 (d, J = 9.52 Hz, 1H, ArH), 7.71-7.69 (m, 9H, meso-ArH), 7.57 (d, J = 8.79
Hz, 1H, CH), 7.10 (dd, J = 8.79, J = 2.20 Hz, 1H, ArH), 7.08 (d, J = 2.20 HZ, 1H, ArH), 6.50
1
2
+
(
d, J = 9.52 Hz, 1H, CH), 5.55 (s, 2H, OCH ); ESI-MS: m/z = 912.1 (M+H) ; Anal. Calcd. for
2
C H N NiO : C, 73.70; H, 3.87; N, 10.74. Found: C, 73.65; H, 4.13; N, 10.46.
56
35
7
3
2
.11.5. Nickel (II) 6-chloro-4-methyl-7-{1-[4-(10,15,20-triphenylporphyrin-5-yl)-phenyl]-1H-
1,2,3]-triazol-4-ylmethoxy}-chromen-2-one (10f)
Reddish brown solid; yield: 94%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 416
[
-4
-1
-1
-1
(
67.50), 529 (4.82) nm; IR (Film) υmax/cm : 2918, 2850, 1731, 1605, 1353, 1274, 1206, 1156,
1
1
047, 1005, 799, 752; H NMR (400 MHz, CDCl ) δ: 8.79-8.71 (m, 8H, β-pyrrolic H), 8.31 (s,
3
1H, triazole H), 8.16 (d, J = 8.05 Hz, 2H, meso-ArH), 8.04-8.00 (m, 8H, meso-ArH), 7.71-7.67
(m, 9H, meso-ArH), 7.58 (s, 1H, ArH), 7.12 (s, 1H, ArH), 6.19 (s, 1H, CH), 5.45 (s, 2H,
13
OCH ), 2.36 (s, 3H, CH ); C NMR (100 MHz, CDCl ) δ: 160.44, 156.08, 153.42, 151.41,
2
3
3
1
1
1
43.56, 142.84, 142.79, 142.69, 142.18, 142.00, 140.70, 136.38, 134.77, 133.67, 132.57,
32.40, 132.35, 131.51, 127.81, 126.89, 125.55, 121.36, 119.37, 119.28, 119.24, 119.04,
+
16.75, 114.40, 113.26, 101.87, 63.37, 18.59; ESI-MS: m/z = 960.1 (M+H) ; Anal. Calcd. for
C H ClN NiO : C, 71.23; H, 3.78; N, 10.20. Found: C, 71.43; H, 3.64; N, 10.21.
57
36
7
3
2
.11.6. Nickel (II) 4-chloromethyl-7-{1-[4-(10,15,20-triphenylporphyrin-5-yl)-phenyl]-1H-
1,2,3]-triazol-4-ylmethoxy}-chromen-2-one (10h)
Reddish brown solid; yield: 91%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 416
[
-4
-1
-1
-1
(
77.49), 529 (5.77) nm; IR (Film) υmax/cm : 3021, 2918, 2850, 1733, 1612, 1441, 1352, 1266,
1
6

ACCEPTED MANUSCRIPT
1
1
138, 1072, 1005, 799, 754; H NMR (400 MHz, CDCl ) δ: 8.79-8.76 (m, 6H, β-pyrrolic H),
3
8.70 (d, J = 4.58 Hz, 2H, β-pyrrolic H), 8.27 (s, 1H, triazole H), 8.15 (d, J = 8.24 Hz, 2H, meso-
ArH), 8.02-8.00 (m, 8H, meso-ArH), 7.73-7.65 (m, 9H, meso-ArH), 7.52 (d, J = 8.70 Hz, 1H,
13
ArH), 7.00-6.97 (m, 2H, ArH), 6.40 (s, 1H, CH), 5.37 (s, 2H, OCH ), 4.56 (s, 2H, CH Cl); C
2
2
NMR (100 MHz, CDCl ) δ: 161.27, 160.53, 155.52, 149.42, 142.84, 142.80, 142.68, 142.15,
3
141.96, 140.68, 136.44, 134.78, 133.66, 132.57, 132.41, 132.35, 131.49, 127.82, 126.90,
125.36, 119.39, 119.25, 119.03, 116.72, 113.01, 112.75, 111.36, 102.50, 62.21, 41.20; ESI-MS:
+
m/z = 960.0 (M+H) ; Anal. Calcd. for C H ClN NiO .H O, C, 69.92; H, 3.91; N, 10.01
57
36
7
3
2
Found: C, 70.13; H, 3.87; N, 9.98.
2
.11.7. Nickel (II) 4-{1-[4-(10,15,20-triphenylporphyrin-5-yl)-phenyl]-1H-[1,2,3]triazol-4-
ylmethoxy}-chromen-2-one (11c)
Purple solid; yield: 95%; mp >300 °C; UV (DMF) λmax (ε×10 , M cm ): 416 (70.68), 530
-4
-1
-1
-1
(
5.11) nm; IR (Film) υmax/cm : 2922, 2851, 1720, 1623, 1458, 1353, 1238, 1106, 1006, 798,
1
7
52; H NMR (400 MHz, CDCl ) δ: 8.79-8.76 (m, 6H, β-pyrrolic H), 8.70 (d, J = 4.58 Hz, 2H,
3
β-pyrrolic H), 8.28 (s, 1H, triazole H), 8.16 (d, J = 6.87 Hz, 2H, meso-ArH), 8.02-8.00 (m, 8H,
meso-ArH), 7.86 (d, J = 7.79 Hz, 1H, ArH), 7.73-7.65 (m, 9H, meso-ArH), 7.56 (t, J = 7.79 Hz,
1
2
1
1
9
4
H, ArH), 7.34 (d, J = 8.70 Hz, 1H, ArH), 7.29-7.26 (m, 1H, ArH), 5.95 (s, 1H, CH), 5.45 (s,
13
H, OCH ); C NMR (100 MHz, CDCl ) δ: 164.96, 162.59, 153.36, 142.86, 142.81, 142.68,
2
3
42.35, 142.14, 140.67, 136.24, 134.80, 133.65, 132.60, 132.44, 132.38, 131.47, 127.83,
26.90, 123.96, 123.12, 123.02, 121.75, 119.40, 119.25, 119.06, 116.80, 116.64, 115.38, 91.67,
+
1.30, 62.58; ESI-MS: m/z = 911.9 (M+H) ; Anal. Calcd. for C H N NiO .H O: C, 72.27; H,
56
35
7
3
2
.01; N, 10.54. Found: C, 72.27; H, 4.13; N, 10.38.
1
7

ACCEPTED MANUSCRIPT
3
. Results and Discussion
3
.1. Synthesis and structure characterization
The synthetic protocol for the preparation of the target meso-phenyl-triazole bridged
porphyrin-coumarin dyads is shown in scheme 3. Initially, 5-(4-azidophenyl)-10,15,20-
triphenylporphyrin (2) was synthesized in 91% yield from 5-(4-aminophenyl)-10,15,20-
triphenylporphyrin (1) according to the modified literature procedure [46] via the
diazotization with H SO /NaNO in THF, followed by in situ reaction with NaN . Then, the
2
4
2
3
corresponding precursor zinc (II) 5-(4-azidophenyl)-10,15,20-triphenylporphyrin (3) was
synthesized from 5-(4-azidophenyl)-10,15,20-triphenylporphyrin (2) by the insertion of zinc
metal after the treatment with zinc acetate in CHCl -MeOH mixture at room temperature
3
(Scheme 1).
<
Insert Scheme 1>
In addition, the coumarin starting materials, 7-ethynylcoumarins (7a-c; Scheme 2) were
synthesized according to reported methods [40, 43]. Initially, the 7-hydroxy coumarins (4a-c)
were converted to the corresponding triflate derivatives (5a-c) by a reaction of
trifluoromethanesulfonic anhydride and triethylamine at 0 °C in dichloromethane. Further,
these molecules underwent Sonogashira coupling with trimethylsilylacetylene in the presence
of PdCl (PPh ) and Et N in DMF at 90 °C to afford trimethylsilyl protected coumarinoalkynes
2
3 2
3
(
6a-c) which on deprotection in the presence of K CO in methanol provided desired 7-
2 3
ethynylcoumarins (7a-c) in 78-81% yields. Also, the coumarinoalkynes (8a-e) were prepared
in good yields by the reaction of compounds (4a-e) with propargyl bromide in acetone
containing K CO at 50 °C according to the literature procedure [44].
2
3
1
8

ACCEPTED MANUSCRIPT
<
Insert Scheme 2>
Then, the novel zinc (II) derivatives of meso-phenyl-triazole bridged porphyrin-coumarin
dyads (9a,c,e, 10a,c,e,g and 11a) were synthesized in 67-87% yields via a Cu (I)-catalyzed
Huisgen 1,3-dipolar cycloaddition reaction of zinc (II) 5-(4-azidophenyl)-10,15,20-
triphenylporphyrin (3) with coumarin substituted alkynes (7a-c or 8a-e). Further, these zinc-
triazoloporphyrin dyads (9a,c 10a,c,e,g and 11a) were demetallated by conc. HCl in
chloroform at room temperature. Interestingly, only free-base porphyin (11b) was found to be
soluble in chloroform and hence it was purified by column chromatography and characterized
spectroscopically, whereas the remaining free-base porphyrins were found to be insoluble in
most of the organic solvents at 25 °C and therefore, used as such for the synthesis of
corresponding nickel porphyrins. Finally, all the free-base porphyrins were converted to the
corresponding nickel analogues (9b,d, 10b,d,f,h and 11c) via the nickel insertion using
Ni(OAc) .4H O in AcOH-CHCl mixture under reflux conditions.
2
2
3
<
Insert Scheme 3>
All the synthesized compounds were characterized on the basis of NMR, IR, UV-Vis and
mass spectral data in addition to elemental analyses. The proton NMR spectra of newly
prepared porphyrin dyads (9a-e, 10a-h and 11a-c) showed a characteristic singlet of one
proton in the downfield region between δ 8.27-9.82 ppm due to a triazole proton and 8 β-
pyrrolic protons for these porphyrins appeared between δ 8.62-8.98 ppm as doublets and
multiplets. Two meso-phenyl protons linked with triazole group were found as a doublet for
two protons between δ 8.15-8.46 ppm whereas 8 meso-phenyl protons of ortho position were
found as doublets and multiplets in the region between δ 7.91-8.38 ppm. The remaining 9
protons of meso-phenyl ring were found as a multiplet between δ 7.47-7.84 ppm. The aryl
protons of coumarin moieties in these compounds were found between δ 5.83-8.23 ppm. In
1
9

ACCEPTED MANUSCRIPT
the porphyrins 10a-h and 11a-c, a characteristic singlet of two protons between δ 5.20-5.55
ppm was present due to -OCH group. In addition, porphyrin 10g and 10h showed a singlet of
2
two protons for the -CH Cl group at δ 5.00 and 4.56 ppm, respectively. In contrast, the
2
porphyrins (9a,b,e and 10a,b,e,f) showed a singlet between δ 2.33-2.50 ppm due to three
methyl protons of coumarin units. A singlet at about δ -2.75 ppm for two protons was
assigned as internal NH protons for the porphyrin 11b. The IR spectrum of the porphyrin 11b
-1
showed a peak at 3317 cm due to N-H bond stretching. In addition, a characteristic peak at
-1
1
677-1736 cm was found in all newly prepared coumarins as well as porphyrin-coumarin
dyads due to C=O bond stretching of coumarin moiety. In addition, the structures of all the
newly synthesized products were further supported by the mass spectral data, which showed
+
the molecular ion peak as (M+H) .
3
3
.3. Photophysical properties
.3.1. UV-Vis spectroscopy
The electronic absorption spectra of zinc analogues of meso-phenyl-triazole bridged
porphyrin-coumarin dyads (9a,c,e, 10a,c,e,g and 11a) displayed a strong Soret bands at ~ 427
nm and two weaker Q-bands at ~ 560 and 601 nm similar to the zinc (II) 5-(4-azidophenyl)-
10,15,20-triphenylporphyrin (3). In contrast, their corresponding nickel derivatives (9b,d,
1
0b,d,f,h and 11c) have shown blue shifted Soret and a Q-band at 416 and 530 nm,
respectively similar to the nickel (II) 5-(4-azidophenyl)-10,15,20-triphenylporphyrin (Ni-N3).
In addition, the free-base porphyrin (11b) showed one strong Soret band at 418 nm and four
Q-bands at 516, 548, 595 and 647 nm similar to the TPP (Soret band at 419 nm and Q-bands
at 516, 550, 595, 647 nm). The UV-Vis absorption spectra of zinc porphyrins (9a, 10a and
1
1a), nickel porphyrins (9b, 10b and 11c) and free-base porphyrin (11b) in DMF are shown
in figure 1. Besides the Soret and Q-bands in porphyrins 9a-b and 10a-b, some additional
peaks were also found at ~ 320 nm due to the presence of coumarin subunits in these
2
0

ACCEPTED MANUSCRIPT
molecules which suggest that there is no significant interaction between the coumarin and
porphyrin subunits in the ground state.
<
Insert Figure 1>
3
.3.2. Fluorescence spectroscopy
The fluorescence spectra of zinc porphyrins (9a,c,e, 10a,c,e,g and 11a) showed two emission
bands at ~ 606 and 659 nm which are slightly intense as compared to the starting porphyrin 3.
The fluorescence bands of nickel porphyrins were found to be very weak under same
experimental conditions. In contrast, the two emission bands at ~ 650 and 718 nm were
observed for free-base porphyrin (11b). The emission spectra of zinc porphyrins (9a, 10a and
11a) and free-base porphyrin (11b) in DMF are shown in figure 2.
<
Insert Figure 2>
Further, in order to analyze the energy transfer behaviour of porphyrin-coumarin dyads (9a,c
and 10a,c), their absorption and emission spectra have been studied. Figure 3a showed the
emission spectra of coumarins 7a,b and porphyrins 9a,c following 320 nm excitation. It was
observed that the fluorescence intensities of coumarin moiety of porphyrins 9a and 9c at ~ 400
nm and porphyrin subunit at ~ 606 and 659 nm have been increased after the formation of
1,2,3-triazole ring as compared to Zn-TPP. Thus, it was concluded that there is an efficient and
rapid intramolecular energy transfer between the porphyrin ring and coumarin subunit in the
porphyrin dyads 9a and 9c. Further, a significant overlapping of the fluorescence spectrum of
7-ethynyl-4-methyl-chromen-2-one (7a) with the absorption spectrum of porphyrin 9a (Figure
3b) also support the above statement as it fulfils the first condition of energy transfer [47].
<
Insert Figure 3>
2
1

ACCEPTED MANUSCRIPT
Interestingly, in the case of porphyrins (10a) and (10c) as shown in figure 4a, the fluorescence
at ~ 400 nm due to coumarin moiety is completely quenched on excitation of porphyrins (10a)
and (10c) at 320 nm and there is an increase in the intensity of fluorescence bands of these
porphyrin dyads at ~ 606 and 659 nm with respect to Zn-TPP. In addition, a significant
overlapping of absorption spectrum of porphyrin (10a) and fluorescence spectrum of 4-methyl-
7-prop-2-ynyloxy-chromen-2-one (8a) was occurred which also revealed an intramolecular
energy transfer from coumarin subunit to the porphyrin core (Figure 4b).
<
Insert Figure 4>
4
. Conclusions
In summary, we have successfully synthesized and characterized five novel coumarin
analogues as starting materials for the synthesis of target porphyrin-coumarin hybrids.
Further, meso-phenyl-triazole bridged porphyrin-coumarin dyads were prepared in 67-95%
isolated yields by combining the porphyrin, 1,2,3-triazole and coumarin moieties in a single
molecular framework via copper (I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction. On
photophysical investigation, a significant intramolecular energy transfer was observed
between coumarin and porphyrin subunits in some of these hybrid molecules. The results
presented in this paper are significantly encouraging and henceforth may be useful for
designing of new porphyrin-coumarin hybrid materials for various applications including
light harvesting and photodynamic agents for photodynamic therapy applications.
Acknowledgements
We thank the University of Delhi, India for providing necessary financial support for this
work. DKS is grateful to Council of Scientific and Industrial Research, New Delhi, India for
providing Senior Research Fellowship. The JEOL ECX 400P (400 MHz) NMR facility at
2
2

ACCEPTED MANUSCRIPT
USIC, University of Delhi and SAIF, CDRI, Lucknow are acknowledged for NMR and mass
spectra, respectively.
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