Synthesis of luminescent rhodium(III) cyclometalated complex by sp2(C)–S bond activation: Application as catalyst in transfer hydrogenation of ketones and live cell imaging

Article abstract of DOI:10.1016/j.molstruc.2019.127524

A new fluorescent Rh(III) cyclometalated complex, [Rh(PPh₃)₂(L)Cl] (1) is synthesized via sp²(C)–S bond activation of a thioether containing azo-phenol ligand (L-SCH₂CH₃). The pseudo octahedral geometry around rhodium is confirmed by single crystal X-ray diffraction method. Cyclic voltammogram of the complex exhibits a quasi-reversible oxidation couple with E_1/2 of 0.74 V (ΔE = 100 mV) along with a quasi-reversible reduction couple (E_1/2 = ?1.18 V, ΔE = 130 mV) in acetonitrile. The complex exhibits low energy emission band at 682 nm with emission quantum yield (? = 0.103) upon excitation at 583 nm. Cytotoxicity of the complex is studied by MTT method with human breast cancer cell lines and IC₅₀ value is found to 18.5 μM. In presence of the complex (10 μM) a bright red fluorescence image of MCF-7 cell lines is observed under fluorescence microscope. Moreover, the complex acts as effective catalyst towards transfer hydrogenation of ketones.

Full text of DOI:10.1016/j.molstruc.2019.127524

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2
Synthesis of luminescent rhodium(III) cyclometalated complex by sp (C)-S bond
activation: Application as catalyst in transfer hydrogenation of ketones and live cell
imaging
Puspendu Roy, Deblina Sarkar, Paramita Ghosh, Chandan Kumar Manna, Nabendu Murmu,
Tapan Kumar Mondal
PII:
S0022-2860(19)31633-3
DOI:
https://doi.org/10.1016/j.molstruc.2019.127524
MOLSTR 127524
Reference:
To appear in:
Journal of Molecular Structure
Received Date:
Accepted Date:
31 October 2019
02 December 2019
Please cite this article as: Puspendu Roy, Deblina Sarkar, Paramita Ghosh, Chandan Kumar
Manna, Nabendu Murmu, Tapan Kumar Mondal, Synthesis of luminescent rhodium(III)
2
cyclometalated complex by sp (C)-S bond activation: Application as catalyst in transfer
hydrogenation of ketones and live cell imaging, Journal of Molecular Structure (2019), https://doi.org
/10.1016/j.molstruc.2019.127524
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Graphical Abstract
Synthesis of luminescent rhodium(III) cyclometalated complex by sp2(C)-S
bond activation: Application as catalyst in transfer hydrogenation of ketones
and live cell imaging
Puspendu Roy, Deblina Sarkar, Paramita Ghosh, Chandan Kumar Manna, Nabendu
Murmu and Tapan Kumar Mondal
A new fluorescent Rh(III) cyclometalated complex, [Rh(PPh3)2(L)Cl] (1) has been synthesized
via sp2(C)-S bond activation of a thioether containing azo-phenol ligand (L-SCH2CH3). The
complex exhibits low energy emission band at 682 nm with high emission quantum yield ( =
0.103). In presence of the complex a bright red fluorescence image of MCF-7 cell lines is
observed under fluorescence microscope. Catalytic activity of complex 1 towards transfer
hydrogenation of ketones is studied.

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Synthesis of luminescent rhodium(III) cyclometalated complex by sp2(C)-S
bond activation: Application as catalyst in transfer hydrogenation of ketones
and live cell imaging
Puspendu Roya,d, Deblina Sarkarb, Paramita Ghoshc, Chandan Kumar Mannaa, Nabendu
Murmuc and Tapan Kumar Mondala*
aDepartment of Chemistry, Jadavpur University, Kolkata-700032, India.
bDepartment of Chemistry, Bagnan College, Howrah, W.B. 711303, India.
cDepartment of Signal Transduction and Biogenis Amines, Chittaranjan National Cancer
Institute, Kolkata- 700026, India
dPresent address: Department of Chemistry, Netaji Nagar Day College, University of Calcutta,
Kolkata – 700092, India.
Abstract
A new fluorescent Rh(III) cyclometalated complex, [Rh(PPh3)2(L)Cl] (1) is synthesized via
sp2(C)-S bond activation of a thioether containing azo-phenol ligand (L-SCH2CH3). The pseudo
octahedral geometry around rhodium is confirmed by single crystal X-ray diffraction method.
Cyclic voltammogram of the complex exhibits a quasi-reversible oxidation couple with E1/2 of
0.74 V (∆E = 100 mV) along with a quasi-reversible reduction couple (E1/2 = -1.18 V, ∆E = 130
mV) in acetonitrile. The complex exhibits low energy emission band at 682 nm with emission
quantum yield ( = 0.103) upon excitation at 583 nm. Cytotoxicity of the complex is studied by
MTT method with human breast cancer cell lines and IC50 value is found to 18.5 M. In
presence of the complex (10 M) a bright red fluorescence image of MCF-7 cell lines is

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observed under fluorescence microscope. Moreover, the complex acts as effective catalyst
towards transfer hydrogenation of ketones.
Key words: Rhodium(III) cyclometalated complex; C-S bond activation; Luminescence property;
Transfer hydrogenation; Live cell imaging; DFT calculation.
Corresponding author: Email: tapank.mondal@jadavpuruniversity.in
1. Introduction
For the last few years, cyclometalated complexes of Rh(III) and Ir(III) are widely studied
because of their outstanding photochemical, photophysical and redox properties [1,2].
They have wide applications as potential photocatalysts, photosensitizers and
photomolecular devices [3,4]. The luminescent Ir(III) complexes are the most researched
class of materials considering their extensive use as the emitters in organic light-emitting
cells and diodes [5-7], sensors [8,9] and in cellular imaging [10,11]. But, similar type of
Rh(III) complexes are rarely studied because of their poor photophysical properties
[12,13]. In the last decades luminescent transition metal complexes have attracted
considerable interest for application in biosensing and cellular imaging study [14].
Cellular imaging offers a unique approach for visualizing morphological details inside the
cell. Although polyaromatic organic chromophores are most widely used as fluorescence
probes in cellular imaging, luminescent metal complexes especially with heavy transition
metals are better probes for bioimaging because of their superior photophysical properties

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with high photostability and relatively long life time. They also exhibit significant Stokes
shifts for easy separation of excitation and emission wavelengths.
In recent years metal mediated C-S bond activation has witnessed a tremendous upsurge
in catalytic reactions [15-17]. The platinum group metal mediated alkyl C(sp3)-S bond cleavage
is widely studied in recent past [18-21], but metal mediated aryl C(sp2)-S bond activation and
formation of cyclometalated complex is rarely studied [22-25]. Herein, we have synthesized
luminescent rhodium(III) cyclometalated complex, [Rh(PPh3)2(L)Cl] (1) via aryl C(sp2)-S bond
cleavage of thioether containing azo-phenol ligand (L-SCH2CH3). The catalytic property of the
complex 1 towards transfer hydrogenation of ketones in i-PrOH was studied. In addition, the
biocompatibility of the complex was checked with human breast cancer cell lines (MCF-7) by in
vitro cytotoxicity assay using MTT. The cell bioimaging study was also carried out in MCF-7
cell lines.
2. Experimental section
2.1. Material and methods
Bis(triphenylphosphine)rhodium(I)carbonyl chloride, [Rh(PPh3)2(CO)Cl] and 2-aminothiophenol
were purchased from Sigma Aldrich. 4-Chloro-2-((2-(ethylthio)phenyl)diazenyl)phenol (L-
SCH2CH3) was prepared following the reported method [26]. Microanalytical data (C, H, N)
were collected on PerkinElmer 2400 CHNS/O elemental analyzer. Infrared spectra were taken on
a RX-1 Perkin Elmer spectrophotometer with samples prepared as KBr pellets. 1H NMR spectra
were recorded on Brucker 300 MHz instrument in CDCl3. HRMS mass spectra were recorded on
Waters (Xevo G2 Q-TOF) mass spectrometer. Electronic spectra were taken on a PerkinElmer
Lambda 750 spectrophotometer. Luminescence property was measured using Shimadzu RF-6000

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fluorescence spectrophotometer at rt (298 K). Cyclic voltammetric measurements were carried
out using a CHI Electrochemical workstation. A platinum wire working electrode, a platinum
wire auxiliary electrode and Ag/AgCl reference electrode were used in a standard three-electrode
configuration. [n-Bu4N][ClO4] was used as the supporting electrolyte in acetonitrile under N2
atmosphere with scan rate of 50 mV/s.
2.2. Synthesis of [Rh(PPh3)2(L)Cl] (1)
0.173 g (0.25 mmol) Rh(PPh3)2(CO)Cl was dissolved in 10 mL acetonitrile. To it 10 mL
acetonitrile solution of 4-chloro-2-((2-(ethylthio)phenyl)diazenyl)phenol (L-SCH2CH3) (0.073 g,
0.25 mmol) was added and the reaction mixture was refluxed for 12 h under N2 atmosphere to
yield a deep blue solution. The solvent was then removed under reduced pressure. The dried
crude product was purified by using a silica gel (mesh 60-120) column. The blue band of 1 was
eluted by 50% (v/v) ethyl acetate-petroleum ether mixture. On removal of the solvent under
reduced pressure the pure complex 1 was obtained as a blue solid which was further dried under
vacuum. Yield, 0.140 g (63%).
Anal. Calc. for C48H37Cl2N2OP2Rh: C, 64.52; H, 4.17; N, 3.13%; Found: C, 64.69; H,
1
4.09; N, 3.07%. IR data (KBr, cm-1): 1410 (N=N). H NMR data (CDCl3, ppm): 7.97 (1H, s),
7.63 (2H, d, J = 7.2), 7.21-7.56 ppm (34H, m). UV-vis in acetonitrile (nm) (, M-1cm-1): 627
(6390), 583 (5637), 535 (sh.), 388 (sh.), 346 (sh.), 291 (25627). em in acetonitrile (ex = 583
nm): 682 nm. HRMS m/z, 893.7215 (M-H+). Cyclic voltammetry (in acetonitrile, scan rate 50
mV/s): E1/2, 0.74 V (∆E = 100 mV) and E1/2, -1.18 V (∆E = 130 mV).
2.3. X-ray crystallography

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Single crystals of 1 were obtained by slow diffusion of n-hexane into dichloromethane solution
of the complex. X-ray data were collected using an automated Bruker AXS Kappa smart Apex-II
diffractometer equipped with an Apex-II CCD area detector using a fine focus sealed tube as the
radiation source of graphite monochromated Mo K radiation ( = 0.71073 Å). Details of crystal
analyses, data collection and structure refinement are summarized in Table 1. Reflection data
were recorded using the  scan technique. The structure was solved and refined by full-matrix
least-squares techniques on F2 using the SHELX-97 [27]. The absorption corrections were done
by multi-scan (SHELXTL program package) and all the data were corrected for Lorentz,
polarization effect. Hydrogen atoms were included in the refinement process as per the riding
model.
2.4. Theoretical study
All calculations were performed with Gaussian 09 program package [28] with the support of the
Gauss View visualization program. Full geometry optimizations were carried out using the
density functional theory (DFT) method at the B3LYP level for the compound [29,30]. All
elements except rhodium were assigned 6-31+G(d) basis set. The LanL2DZ basis set with
effective core potential (ECP) set of Hay and Wadt was used for rhodium atom [31-33]. Vertical
electronic excitations based on B3LYP optimized geometries were computed using the time-
dependent density functional theory (TDDFT) formalism [34-36] in acetonitrile using conductor-
like polarizable continuum model (CPCM) [37-39].
2.5. Procedure for catalytic transfer hydrogenation
In a typical experiment the ketone (3 mmol), KOH (0.1 mmol), and rhodium(III) complex (1)
(0.006 mmol) were added to 10 mL of i-PrOH, and the mixture was stirred at 80 °C in an inert
atmosphere. The reaction was then monitored at various time intervals by the use of GC. After

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the reaction was complete, i-PrOH was removed on a rotary evaporator, and the resulting
semisolid was extracted with diethyl ether (5 × 10 mL). The extract was passed through a short
column of silica gel. The column was washed with ∼100 mL of diethyl ether. All the eluates
from the column were mixed, and the solvent from the mixture was evaporated off on a rotary
evaporator. The resulting residue was dissolved in 2-3 mL of hexane. Conversions were
determined by GC instrument equipped with a flame ionization detector (FID) using a HP-5
column of 30 m length, 0.53 mm diameter and 5.00 m film thickness. The column, injector and
detector temperatures were 200, 250 and 250 ºC respectively. The carrier gas was N2 (UHP
grade) at a flow rate of 30 mL/min. The injection volume of sample was 2 L. The alcohols were
identified by GC using undecane as an internal standard and each of the catalytic run was
performed three times.
2.6. In vitro cell imaging
2.6.1. Cell Survivability assay
Human breast cancer cell lines MCF-7 were evaluated for cytotoxicity with rhodium(III)
complex, [Rh(PPh3)2(L)Cl] (1). MCF-7 cell lines were obtained from National centre for cell
science, Pune, India and maintained in Minimum Essential Media Earle’s (MEM) (Gibco, life
technologies) supplemented with 10% Fetal Bovine Serum (FBS) (Gibco, life technologies,
USA) and stored at 37 °C in a humidified incubator under 5% CO2 atmosphere. Cells were
seeded in 96-well plates at a density of 5103 cells per well and cultured in CO2 incubator for 24
h. The cells were treated with increasing doses complex concentrations (5, 10, 20, 25, 30, 50, 75,
100) M, along with control. Complex 1 was dissolved in DMSO but the final concentration of
DMSO while treatment of cells was maintained below 1%. After treatment for 24 h, Methyl
tetrazolium dye (MTT) (5 mg/ml) solution was added to each well (10 L/well). The plates were

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incubated in the dark at 37 C for 2 h. To each well 100 L DMSO was added and allowed to
stand for 1 h in a vortex shaker. Cell viability determination was studied by recording absorbance
at 570 nm for each well using a microplate reader (Tecan, infinite M200). Untreated cells were
served as 100% viable. Linearly fitted plot between complex concentration and O.D value at 570
nm was generated for determination of IC50 value of the free receptor. Concentration of the
complex resulting in 50% death after 24 h treatment was obtained as the IC50 value.
2.6.2. Live cell imaging
Cultured cells were then grown on 22×22 mm glass cover slip placed on the bottom of six well
plates and treated with 10 µM of complex for 12 h. The selected dose (10 µM) was less than
LD50 which was found to be 18.53 µM. After 12 h, media were discarded and 500 µl methanol
added, kept for 15 min for fixation. Finally the cells were washed with 0.5 % Phosphate buffer
saline Tween (PBST) twice and then with 1PBS thrice. The cover slips were mounted on slides
using glycerol. The slides were observed under fluorescent microscope (Leica DM4000 B,
Germany) under 20X magnification.
3. Results and discussion
3.1. Synthesis and formulation
The thioether containing tridentate O, N, S donor ligand, 4-chloro-2-((2-(ethylthio)phenyl)
diazenyl)phenol (L-SCH2CH3) was synthesized as air stable red solid by diazo-coupling of 2-
(ethylthio)benzenamine with 4-chlorophenol following the reported method [26].
Stoichhiometric reaction between L-SCH2CH3 and Rh(PPh3)2(CO)Cl in acetonitrile under
refluxing condition yielded deep blue product (scheme 1). The complex was thoroughly
1
characterized by several spectroscopic techniques. H NMR spectrum of the complex was taken

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CDCl3. The significant observation in the spectrum of the complex is the disappearance of S–
CH2CH3 resonances due to cleavage of C-S bond. The structure of the complex is
unambiguously determined by single crystal X-ray diffraction method. Interestingly, instead of
cleavage of sp3(C)-S bond [40], the sp2(C)-S bond is cleaved followed by removal of SCH2CH3
group and a direct Rh-C(aryl) bond formation is taking place in the complex. Due to
desulfurization the modified ligand is coordinated as tridentate fashion to rhodium centre through
azo-N, phenolic-O and aryl-C atom.
Cl
S
PPh3
[Rh(PPh3)2(CO)Cl]
O
N
N
N
N
OH
Cl
Reflux in acetonitrile
for 12 h
Rh
Cl
PPh3
1
[Rh(PPh3)2(L)Cl] ( )
L
-SCH2CH3
Scheme 1. Synthesis of [Rh(PPh3)2(L)Cl] (1) by C-S bond cleavage of L-SCH2CH3
3.2. Crystal structure
The geometry of the complex was ascertained by single crystal X-ray diffraction method. Single
crystals were grown by slow diffusion of dichloromethane solution of the complex into hexane at
rt. The X-ray crystallographic data collection and refinement parameters of 1 are given in Table
1. Selected bond lengths and bond angles are summarized in Table 2. ORTEP plot of the
molecular structure with the atomic numbering scheme for 1 is shown in Fig. 1. The rhodium
atom adopts a distorted octahedral geometry and is coordinated by two PPh3 groups in trans

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positions of the octahedron, the modified chelating ligand (L) coordinated through phenolic-O,
azo-N and aryl-C atoms. The vacant position of the square plane is occupied by chlorine atom.
The deviation of the rhodium coordination sphere from the ideal octahedron is because of the
small bite angles of the five membered chelate rings (Rh1-C1-C6-N2-N1) (78.97(17)°) and
(Rh1-N1-C7-C12-O1) (80.25(14)°). The Rh-P (Rh1-P1, 2.4085(13) and Rh1-P2, 2.4288(14) Å),
Rh-Cl (Rh1-Cl1, 2.4108(13) Å) and Rh-C (Rh1-C1, 2.023(4) Å) bond distances are found as
expected for similar rhodium phosphine complexes [25, 41-43]. The azo, N-N bond distance in
the complex is found to be elongated (N1-N2, 1.304(5) Å) supporting dπ(RhIII)π*(N=N) back
donation.
3.3. Absorption and emission spectra
The UV-vis spectrum of the complex 1 in acetonitrile exhibits two closed by low energy bands at
627 nm ( = 6390 M-1cm-1) and 583 nm ( = 5637 M-1cm-1) along with a shoulder at 535 nm. In
addition a high energy sharp band is observed at 291 nm ( = 25627 M-1cm-1) along with the
shoulder at 346 nm and 388 nm. Upon excitation at 583 nm in acetonitrile the complex exhibits
very strong emission spectrum with max at 682 nm (Fig. 2). The emission quantum yield () of
the complex is found to be 0.103. Lifetime data of the emission decay curve was deconvoluted
with respect to the lamp profile. The observed emission decay fits with bi-exponential profile
with χ2 = 1.106 (Fig. 3). We have used mean fluorescence lifetime (f = a1 + a22, where a1 and
a2 are relative amplitude of decay process) to study the excited state stability of the complex. The
emission lifetime of the complex is found to be 2.26 ns.
3.4. DFT and TDDFT calculation
The full geometry of the complex 1 was optimized by DFT method in singlet ground state using
the B3LYP correlation functional. The optimized bond parameters for complex 1 are given in

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Table 2. The calculated bond distances and angles are well correlated with the X-ray crystal
structure data.
The contour plots of selected molecular orbitals are given in Fig. 4. Energy and % of
composition is summarized in Table 3. HOMO of the complex is found to be 93% π(L) character
and concentrated on phenolate moiety of the ligand along with very minor contribution of dπ(Rh)
orbital. HOMO-1 and HOMO-2 have mixed dπ(Rh), π(L) and pπ(Cl) character. The low energy
unoccupied molecular orbital (LUMO) has 93% π*(L) character with major contribution of
π*(N=N) orbital. The significant contribution of dπ(Rh) along with π(PPh3) orbitals is found to
be in LUMO+1 and LUMO+2 of the complex.
To interpret the electronic spectra, singlet-singlet vertical electronic excitations were
calculated by TDDFT/CPCM method in acetonitrile. Strong HOMO to LUMO transition is
found to be at 593 nm (f = 0.1683) having ILCT character. One low energy weak transition
corresponding to HOMOLUMO+1 transition (LMCT/ILCT character) at 515 nm is observed
(Table 4). The high energy transition of the complex at 326 nm (f = 0.3676) corresponding to the
experimental band at 291 nm.
3.5. Electrochemistry
The electrochemical behavior of the complex was investigated by cyclic voltammetry (CV) in
presence of [n-Bu4N][ClO4] in acetonitrile at scan rate 50 mVS-1. In the potential window 1.5 to -
1.5 V complex 1 exhibits one quasi-reversible oxidation couple with E1/2 of 0.74 V (∆E = 100
mV) along with one quasi-reversible reduction couple (E1/2 = -1.18 V, ∆E = 130 mV) positive
and negative to the reference electrode respectively (Ag/AgCl) (Fig. 5). The redox behavior of
the complexes is interpreted by DFT study. HOMO of the complex has 93% π(L) character with
major contribution of phenolate moiety of the ligand, so the oxidation of the complex is assigned

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as oxidation of phenolate moiety to form phenoxyl radical [19,44]. LUMO of the complex has
93% ligand character with major contribution of π*(N=N) orbital. Therefore the reduction of the
complex is assigned as the reduction of azo(N=N) bond to form azo anion radical (L/L−) as
expected.
3.6. Catalytic transfer hydrogenation
The transfer hydrogenation is an important and efficient reaction in organic synthesis. So far
many rhodium(III) complexes were used as effective catalysts for transfer hydrogenation
reactions [21,43], which encourage us to use our synthesized Rh(III) cyclometalated complex as
catalyst for the transfer hydrogenation of ketones.
Initially to optimize the reaction condition, catalytic efficiency of complex 1 for the
conversion of acetophenone to 1-phenylethanol was tested in iPrOH with the variation of catalyst
to substrate ratio (C:S), reaction time and different bases and the results are summarized in Table
5. The conversion was found to be effective in presence of strong base KOH in comparison to
Na2CO3, CH3COONa or KOtBu. Again, to understand the catalytic efficiency of the complex 1,
different catalyst:substrate (C:S) ratios were tested in the transfer hydrogenation of acetophenone
in i-PrOH/KOH. It is found that the conversion is maximum in C:S ratio of 1:300. With the
variation of C:S ratio to 1:400 to 1:1500, the reaction still proceeds but a sharp decrease in rate
of conversion is observed for C:S ratio 1:600 to 1:1500. The conversion is excellent with
appreciable turnover number (TON) when the C:S ratio is 1:500 and hence this C:S ratio is the
best choice for catalytic transfer hydrogenation reactions for complex 1. Again, to understand the
effect of the catalyst, the reactions were also carried out in absence of the Rh(III) complex but no
significant catalytic conversions were observed. A series of ketones were screened in transfer
hydrogenation reaction using the optimum condition, C:S ratio of 1:500 and KOH as base. The

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results are summarized in Table 6. The maximum conversions were observed for 1-(4-
chlorophenyl)ethanone (99%), acetophenone (98%), 1-(p-tolyl)ethanone (98%) and p-
nitroacetophenone (98%). The conversions of other acetophenones were found to be in the range
of 91-97%. The catalytic efficiency of the present rhodium(III) cyclometalated complex is found
to be very competitive with the reported transfer hydrogenation catalysts [45-47].
3.7. Cell bio-imaging
A yellow coloured tetrazolium salt MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide) was used to quantify mammalian cell survivability and proliferation. Mitochondria of
viable cells reduce it to a non-fluorescent insoluble formazan, purple colour dye. Thus the degree
of viability of cells can be determined by measuring the absorbance of the purple coloured
solution at 570 nm. MTT experiment establishes that the rhodium(III) complex has moderate
toxicity on human breast cancer cell line MCF-7 (Fig. 6). The IC50 value of the complex on
MCF-7 cell line is found to be 18.53 M. The chosen dose was taken to be lower than the IC50
value of the complex at 10 M concentration. Upon incubation of MCF-7 cells with the complex
causes a striking red fluorescence in the intracellular region (Fig. 7). This observation clearly
indicates that the present luminescent rhodium(III) complex may be used as biomarker for
fluorescence imaging. Through bright field images, it is observed that the treated cells do not
show any distinct or visible morphological changes indicating that the cells are viable in the used
concentration of the complex.
4. Conclusion
Herein, we have synthesized a new fluorescent Rh(III) cyclometalated complex,
[Rh(PPh3)2(L)Cl] (1) via C-S bond activation of a thioether containing azo-phenol ligand (L-
SCH2CH3). The distorted octahedral geometry of the complex is confirmed by X-ray structure.

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The complex exhibits a quasi-reversible oxidation couple (E1/2 = 0.74 V, E = 100 V) along with
quasi-reversible reduction peak at E1/2 = -1.18 V (∆E = 130 mV). The complex exhibits low
energy emission band at 682 nm with high emission quantum yield ( = 0.103). Cytotoxicity of
the complex is studied by MTT method with human breast cancer cell lines (MCF-7) and IC50
value is found to be 18.5 M. In presence of the complex (10 M) a bright red fluorescence
image of MCF-7 cell lines is observed under fluorescence microscope. The complex exhibits
efficient catalytic activity towards transfer hydrogenation of ketones.
Acknowledgment
Financial supports received from the Science and Engineering Research Board (SERB), New
Delhi, India (EEQ/2018/000266) is gratefully acknowledged. P. Roy and R. Naskar are thankful
to UGC, New Delhi, India for fellowship. C. K. Manna is grateful to RUSA 2.0 programme for
fellowship.
Supplementary materials
Crystallographic data for the structure of 1 has been deposited with the Cambridge
Crystallographic Data center, CCDC No. 1496012. Copies of this information may be obtained
free of charge from the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (e-mail:
deposit@ccdc.cam.ac.uk or www:htpp://www.ccdc.cam.ac.uk).
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Table 1. Crystallographic data for [Rh(Cl)(PPh3)2(L)] (1)
Formula
C48H37Cl2N2OP2Rh
Formula Weight
Crystal System
Space group
893.55
Monoclinic
P21/c
a, b, c [Å]
12.6327(5), 19.1782(7), 18.7752(6)
β
109.558(2)
4286.3(3)
4
V [ Å3]
Z
D(calc) [g/cm3]
Mu(MoKa) [ /mm]
F(000)
1.385
0.636
1824
Crystal Size [mm]
Temperature (K)
Radiation [Å]
θ(Min-Max) [°]
Dataset (h; k; l)
Total, Unique Data, R(int)
Observed data [I > 2σ(I)]
Nref, Npar
293(2)
0.71073
2.01- 27.25
-15 and 15; -24 and 23; -24 and 24
66181, 9459, 0.0880
5716
9459, 506
0.0666; 0.1576
1.031
R1, wR2[I >2(I)]
GOF
Largest diff. Peak/hole, (e Å─3)
-1.290; 1.617

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Table 2. Some selected bond distances (Å) and angles (°) of [Rh(Cl)(PPh3)2(L)] (1)
Bonds(Å)
Rh1-N1
Rh1-C1
Rh1-O1
Rh1-P1
Rh1-P2
Rh1-Cl1
N1-N2
X-ray
Calc.
2.006
2.016
2.278
2.457
2.457
2.445
1.277
1.298
1.391
1.429
1.972(3)
2.023(4)
2.220(3)
2.4085(13)
2.4288(14)
2.4108(13)
1.304(5)
1.327(6)
1.416(6)
1.423(6)
O1-C12
N1-C7
C1-C6
Angles(o )
N1-Rh1-C1
N1-Rh1-O1
C1-Rh1-O1
N1-Rh1-P1
C1-Rh1-P1
O1-Rh1-P1
N1-Rh1-P2
C1-Rh1-P2
O1-Rh1-P2
O1-Rh1-Cl1
N1-Rh1-Cl1
C1-Rh1-Cl1
78.97(17)
80.25(14)
159.19(16)
90.36(11)
91.27(14)
89.98(10)
95.60(11)
91.40(14)
89.50(10)
100.83(10)
178.62(11)
99.97(14)
79.252
78.009
157.262
93.349
92.094
89.231
93.350
92.094
89.233
102.099
179.890
100.638

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Table 3. Energy and compositions of some selected molecular orbitals of 1
MO
Energy
% Composition
Rh
01
01
01
29
33
04
05
35
11
14
09
06
02
01
02
02
10
PPh3
95
98
94
47
54
03
02
03
34
12
40
38
76
97
92
82
78
L
Cl
0
LUMO+5
LUMO+4
LUMO+3
LUMO+2
LUMO+1
LUMO
-0.55
-0.60
-0.61
-0.84
-1.70
-2.27
-4.98
-5.78
-5.91
-6.20
-6.26
-6.36
-6.62
-6.69
-6.70
-6.84
-6.86
03
0
01
0
05
20
08
93
93
27
26
53
51
42
12
02
03
12
10
04
05
0
HOMO
0
HOMO-1
HOMO-2
HOMO-3
HOMO-4
HOMO-5
HOMO-6
HOMO-7
HOMO-8
HOMO-9
HOMO-10
36
29
21
0
14
09
01
03
04
02

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Table 4. The experimental absorption bands and the electronic transitions calculated with the
TDDFT/B3LYP/CPCM method for complex 1
Osc.

expt. (nm)
E (eV) Strength (f) Key excitations
Character
ILCT
(nm)
593.3
515.2
414.1
375.4
365.0
352.5
337.8
326.2
(ε (M-1cm-1))
2.0896 0.1683
2.4064 0.0108
2.9939 0.0104
3.3028 0.0366
3.3971 0.0641
3.5175 0.0625
3.6702 0.1418
3.8009 0.3676
627 (6390)
(97%)HOMOLUMO
LMCT/ILCT 583 (5637)
(93%)HOMOLUMO+1
(96%)HOMO-1LUMO
(67%)HOMO-3LUMO
(82%)HOMO-4LUMO
(62%)HOMO-2LUMO+3
(69%)HOMO-3LUMO+3
(72%)HOMO-5LUMO
MLCT
ILCT
ILCT
ILCT
ILCT
ILCT
535 (sh)
388 (sh)
346 (sh)
291 (25627)

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Table 5. Effect of C:S ratio, base and reaction time on the transfer hydrogenation of
acetophenonea
O
OH
1
Complex
i-PrOH, Base
Entry C:S ratio Base
Time (h)
Conversionb (%) TONc
67
1
1:300
1:300
1:300
1:300
1:300
1:300
1:300
1:300
1:300
1:400
1:500
1:600
1:800
1:1000
1:1500
KOH
KOH
KOH
KOH
KOH
NaOH
Na2CO3
3
202
244
296
297
297
287
158
128
200
392
488
506
548
428
398
2
4
81
99
99
99
96
53
43
67
98
98
84
69
43
25
3
5
4
7
5
10
5
6
7
5
8
CH3COONa 5
9
KOtBu
KOH
KOH
KOH
KOH
KOH
KOH
5
5
5
5
5
5
5
10
11
12
13
14
15
aReaction condition: acetophenone (3 mmol), complex 1 (10-2 mol), catalyst:KOH 1:4 in i-
b
PrOH (10 mL) at 80 ºC; Conversions were determined by GC with undecane as an internal
c
standard and were reported mean values of three runs; Turnover number (TON) = mole of
product/mol of catalyst.

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Table 6. Transfer hydrogenation of ketones using complex 1a
1
Complex
O
OH
OH
R2
O
C : S = 1: 500
+
+
R1
R2
R1
KOH, Reflux for 5 h
Entry
1
Ketones
Alcohols
Conversion
TONc
488
(%)b
98
O
OH
O
O
OH
OH
2
3
94
95
472
476
O
O
OH
OH
4
5
96
94
479
468
O
OH
6
7
92
98
458
491
O
OH
OH
OH
O
8
9
99
97
493
493
Cl
Cl
Br
O
O
Br
OH
10
98
492
O2N
O2N
aExperimental condition: reactions were carried out at 80 °C, ketone (3 mmol), Rh(III) complex
b
(0.2 mol%), KOH (0.1 mmol), i-PrOH (10 mL); Conversions were determined by GC with
undecane as an internal standard and were reported mean values of three runs; cTurnover number
(TON) = mole of product/mol of catalyst

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Figure captions
Fig. 1. ORTEP plot with 35% ellipsoidal probability of 1
Fig. 2. UV-vis () and emission () spectra of complex 1 in acetonitrile
Fig. 3. Life time decay profile of 1 () (ex = 490 nm) and prompt (■■■) in acetonitrile
Fig. 4. Contour plots of selected molecular orbitals of 1
Fig. 5. Cyclic voltammogram of 1 in acetonitrile with respect to Ag/AgCl reference electrode
([n-Bu4N][ClO4] was used as the supporting electrolyte)
Fig. 6. MTT assay of complex 1 on MCF-7 cell line
Fig. 7. (a) Fluorescence image, (b) bright field image and (c) merged image of human breast
cancer cell lines (MCF-7) in presence of complex 1

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Fig. 1
35
30
25
20
15
10
5
0
300 400 500 600 700 800 900
 nm
Fig. 2

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Fig. 3
HOMO
HOMO-1
HOMO-2
LUMO
LUMO+1
Fig. 4
LUMO+2

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Fig. 5
120
100
80
60
40
20
0
Conc. in M
Fig. 6

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a
b
c
Fig. 7

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There are no conflicts of interest to declare.