Anticancer Activity of Iridium(III) Complexes Based on a Pyrazole-Appended Quinoline-Based BODIPY

Article

pubs.acs.org/IC

Anticancer Activity of Iridium(III) Complexes Based on a Pyrazole-

Appended Quinoline-Based BODIPY

Rajendra Prasad Paitandi,^†Sujay Mukhopadhyay,^†Roop Shikha Singh,^†Vinay Sharma,^‡

Shaikh M. Mobin,^‡,§,∥and Daya Shankar Pandey*^,†

^†Department of Chemistry, Institute of Science, Banaras Hindu University, Varanasi 221005, Uttar Pradesh, India

^‡Centre for Biosciences and Bio-Medical Engineering, ^§Discipline of Chemistry, and ^∥Metallurgical Engineering and Material Science,

Indian Institute of Technology Indore, Simrol, Indore 453552, India

S

* Supporting Information

ABSTRACT: A pyrazole-appended quinoline-based 4,4-diﬂuoro-4-bora-3a,4a-

diaza-s-indacene (L1, BODIPY) has been synthesized and used as a ligand for

the preparation of iridium(III) complexes [Ir(phpy)₂(L1)]PF₆(1; phpy = 2-

phenylpyridine) and [(η⁵-C₅Me₅)Ir(L1)Cl]PF₆(2). The ligand L1 and

complexes 1 and 2 have been meticulously characterized by elemental analyses

1

and spectral studies (IR, electrospray ionization mass spectrometry, H and

¹³C NMR, UV/vis, ﬂuorescence) and their structures explicitly authenticated

by single-crystal X-ray analyses. UV/vis, ﬂuorescence, and circular dichroism

studies showed that complexes strongly bind with calf-thymus DNA and

bovine serum albumin. Molecular docking studies clearly illustrated binding

through DNA minor grooves via van der Waals forces and their electrostatic

interaction and occurrence in the hydrophobic cavity of protein (subdomain

IIA). Cytotoxicity, morphological changes, and apoptosis have been explored

by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and Hoechst 33342 staining. IC₅₀values for

complexes (1, 30 μM; 2, 50 μM) at 24 h toward the human cervical cancer cell line (HeLa) are as good as that of cisplatin (21.6

μM) under analogous conditions, and their ability to kill cancer cells lies in the order 1 > 2. Because of the inherent emissive

nature of the BODIPY moiety, these are apt for intracellular visualization at low concentration and may ﬁnd potential

applications in cellular imaging and behave as a theranostic agent.

anticancer potencies besides their luminescent properties.²³⁻²⁶

In this regard, cyclometalated iridium(III) complexes, because

INTRODUCTION

■

The successful application of cisplatin and its derivatives in the

of their high quantum yield, large Stokes shift, long-lived

treatment of a broad spectrum of cancers has stimulated the

luminescence, good photostability, and cell permeability, have

scientiﬁc community to develop other metal complexes

attracted the attention of many research groups.^27−33,33In

exhibiting better anticancer activity.¹⁻⁶Despite outstanding

addition, these enhance the electron density at the metal center

utility, the clinical value of platinum-based drugs is severely

and make it labile along with stabilizing high-valent metal

aﬀected by serious side eﬀects like high toxicity, drug selectivity,

and intrinsic and acquired resistance.⁷⁻⁹To overcome these

complexes and augmenting the oxidizing ability via reactive

oxygen species generation, causing cancer cell death.³⁵⁻³⁷The

problems, metallodrugs containing organometallic moieties,

incorporation of an electron-rich pentamethylcyclopentadienyl

metallocenes, and half-sandwich complexes have drawn special

attention.^1,5,10−16In this direction, the antiproliferative activity

moiety can have power over the balance between the

hydrophobicity and hydrophilicity and enhance cellular

of some organometallic square-planar iridium(I) complexes,

uptake.³⁸It is worth mentioning that cationic iridium(III)

viz., [Ir(acac)(cod)], [IrCl(cod)]₂, etc., has been examined

against various types of cancer.^17,18Although these exhibit

complexes can regulate covalent or noncovalent intercalation/

interactions and augment anticancer activity because of their

promising antiproliferative activity, their mechanism of action

speciﬁc redox properties.³⁹⁻⁴⁶Thus, numerous half-sandwich

cyclopentadienyliridium(III) complexes containing bidentate

ligands (N^N, N^O, or C^N chelating) have been synthesized

and shown to be extremely eﬀective toward tumor cells.^11,47−50

Sadler et al. observed that replacement of the neutral N^N-

donor 2,2′-bipyridine (bpy) by C^N-chelating 2-phenylpyridine

has not been established with certainty.⁹Considering this and

the high stability of iridium(III) complexes, coupled with the

signiﬁcant structural diversity half-sandwich iridium(III)

complexes, has been fascinating because some of these

exhibited encouraging results. Additionally, it has been

categorically shown that their action involves both an attack

on DNA and a perturbation in the redox status of the cells.¹⁹⁻²²

Furthermore, multifunctional theranostic agents have

garnered signiﬁcant clinical relevance because of their

Received: July 3, 2017

A

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

Scheme 1. Syntheses of Ligand L1 and Complexes 1 and 2

(phpy) in [(η⁵-C₅Me₅)Ir(bpy)Cl]⁺improved its cytotoxic

behavior against A2780 cells.^10,49Also, they have thoroughly

investigated the eﬀect of changes of the negatively charged

C^N-chelating ligand and the nature of diverse cyclo-

pentadienyl groups on the biological properties.^11,48,50

cytotoxicity against human cervical cancer cell line (HeLa)

along with possible applications as a theranostic agent.

RESULTS AND DISCUSSION

■

Synthesis and Characterization. A methoxy derivative of

2-chloroquinoline-3-carbaldehyde has been synthesized by

following literature procedures.⁵⁹6-Methoxy-2-(1H-pyrazol-1-

yl)quinoline-3-carbaldehyde (A) was prepared by treating a

solution of a quinoline aldehyde (2-chloroquinoline-3-carbalde-

hyde) in toluene with pyrazole under reﬂuxing conditions and

continual stirring (48 h). Aldehyde A reacted with an excess of

pyrrole in the presence of triﬂuoroacetic acid to aﬀord 5-[6-

methoxy-2-(1H-pyrazol-1-yl)quinoline]dipyrromethane (B).

The synthesis of L1 was achieved from B via a two-step

reaction: ﬁrst oxidation to the corresponding dipyrrin using 2,3-

dicloro-5,6-dicyano-1,4-benzoquinone and subsequent com-

plexation with boron upon treatment with boron triﬂuoride

etherate (BF₃·Et₂O) in the presence of triethylamine (35%

yield; Scheme 1).⁶⁰Reactions of the ligand L1 with chloro-

bridged dimeric precursors [(phpy)₂Ir(μ-Cl)]₂and [{(η⁵-

C₅Me₅)Ir(μ-Cl)Cl}₂] in dichloromethane/methanol (1:1)

under stirring conditions (room temperature, 16 h) aﬀorded

cationic complexes 1 and 2 in good yield (70−80%). These

were isolated as their hexaﬂuorophosphate salt by adding a

saturated solution of NH₄PF₆in methanol. A simple synthetic

strategy adopted for the preparation of A, B, ligand L1, and

complexes 1 and 2 is shown in Scheme 1.

Additionally, intercalation of the drugs with a DNA helix

inhibits enzyme replication.^51,52Dipyrrin and its derivatives

(4,4-diﬂuoro-4-bora-3a,4a-diaza-s-indacene, BODIPY) are

known to intercalate between base pairs of DNA and interfere

with the transcription process, which can be exploited in the

design of anticancer drugs.^53,54Further, BODIPY dyes have

been used as potential photodynamic therapeutic agents

because of their ability to generate singlet oxygen.⁵⁵Recently,

Lee et al. developed some ruthenium(II), palladium(II), and

iridium(III) metallarectangles containing a BODIPY-based

linker and established that these exhibit highly selective

anticancer activity, strongly interact with DNA and protein,

and also display cellular localization.^41,56We too have prepared

some iridium(III) dipyrrinato complexes possessing diverse

substituents like thioether, ferrocenyl, 2-methoxypyridyl, etc.,

and have shown that these interact with DNA and protein and

exhibit prominent anticancer activity.^53,57,58To develop

eﬃcient anticancer agents based on BODIPY-containing

iridium(III) complexes through this work, we prepared a

novel pyrazole-appended quinoline-based BODIPY (L1) and

utilized it in the synthesis of cationic complexes [Ir-

(phpy)₂(L1)]PF₆(1; phpy = 2-phenylpyridine) and [(η⁵-

C₅Me₅)Ir(L1)Cl]PF₆(2). Through this contribution, we

present the synthesis and thorough characterization of L1

and cationic iridium(III) complexes 1 and 2. Also, we describe

herein their binding ability with DNA and protein and

The complexes under study are unaﬀected by air and

moisture, soluble in common organic solvents like methanol,

ethanol, acetone, dimethylformamide, dimethyl sulfoxide

B

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

Table 1. Crystal Data and Structure Reﬁnement Parameters for L1, 1, and 2

crystal param

L1

1

2

empirical formula

fw

C₆₆H₄₇B₃F₆N₁₅O₃

1244.61

C₄₄H₃₂BF₈IrN₇OP

C₃₂H₃₁BClF₈IrN₅OP

923.05

1061.20

cryst syst

space group

a (Å)

triclinic

monoclinic

triclinic

P1

̅

C2/c

P1

̅

10.9626(3)

24.3469(5)

10.0848(3)

11.5614(4)

17.1320(4)

95.205(2)

91.872(2)

99.623(2)

1958.94(1)

red, block

2

b (Å)

15.8202(4)

15.2786(3)

c (Å)

18.2066(6)

26.9194(5)

α (deg)

β (deg)

γ (deg)

V (Å³)

109.971(3)

90.00

97.368(2)

102.173(2)

94.100(2)

90.00

2920.59(2)

9788.5(3)

color and habit

Z

d_calcd(g cm⁻³

red, needle

red, block

2

4

)

1.415

1.562

1.565

temperature (K)

293(2)

150(2)

293(2)

wavelength (Å)

1.54184

0.71073

1.54184

8.230

μ (mm⁻¹

)

0.862

2.830

GOF on F²

1.033

1.090

1.046

R indices (all data)

ﬁnal R indices [I > 2σ(I)]

R1 = 0.0556, wR2 = 0.1573

R1 = 0.0673, wR2 = 0.1677

R1 = 0.0532, wR2 = 0.1472

R1 = 0.0758, wR2 = 0.1734

R1 = 0.0584, wR2 = 0.1643

R1 = 0.0601, wR2 = 0.1676

Figure 1. ORTEP views of L1, 1, and 2 at 30% thermal ellipsoid probability (H atoms are omitted for clarity).

(DMSO), acetonitrile, dichloromethane, chloroform, and

water, and insoluble in diethyl ether, hexane, and petroleum

ether. These have been meticulously characterized by

satisfactory elemental analyses and spectroscopic studies

BODIPY proton resonances exhibit a downﬁeld shift relative to

free BODIPY. Moreover, protons due to the metal precursor

exhibit an upﬁeld shift in the complexes relative to precursors

[{(phpy)₂Ir(μ-Cl)}₂and {(η⁵-C₅Me₅)Ir(μ-Cl)Cl}₂]. The rela-

tive shifts and intensities of the ligand and η⁵-bonded

hydrocarbon protons aﬃrm the coordination of BODIPY

with the metal center and formation of the complexes. In an

analogous manner, ¹³C NMR spectral data of 1−2 further

support the formation of these complexes.

Mass Spectral Studies. The composition and stability of

L1 and complexes 1 and 2 were investigated by ESI-MS (Figure

S5). In its mass spectrum, L1 displays a molecular ion peak at

m/z 438.1351 (calcd m/z 438.1314) due to (M + Na)⁺.

Complexes 1 and 2 exhibit molecular ion peaks at m/z

937.1200 (calcd m/z 937.1000) due to (M − PF₆)⁺and m/z

778.2 (calcd m/z 778.1) due to (M − PF₆)⁺, respectively,

arising as a result of loss of the counteranion hexaﬂuoropos-

phate. Further, formulation of the ligand and complexes has

been veriﬁed by determination of their crystal structures.

Crystal Structures. The structures of L1, 1, and 2 have

been determined by single-crystal X-ray analyses. Details about

data collection, solution, and reﬁnement are given in the

Experimental Section and Table 1. The ligand L1 crystallizes in

1

[electrospray ionization mass spectrometry (ESI-MS), H and

¹³C NMR, UV/vis, and ﬂuorescence]. Crystal structures of L1,

1, and 2 have been determined by single-crystal X-ray analyses.

Structures of 1 and 2 have also been optimized theoretically

using geometrical coordinates from their crystallographic data.

NMR Spectral Studies. To aﬃrm the formula, purity, and

1

integrity of these compounds, H and ¹³C NMR spectra have

been acquired in CDCl₃at room temperature. The resulting

data are summarized in the Experimental Section and the

1

spectra depicted in Figures S1 −S4. H NMR spectra of B

display peaks due to methoxy (δ 3.87), meso (δ 6.29), pyrrolic

[δ 5.89, 6.11, 6.70, and 9.07 (br, NH)], aromatic and pyrazole

1

protons (δ 6.46, 6.99, 7.33, 7.79, 7.88, 8.15, and 8.19). H

NMR spectra of L1 show a loss of the resonances due to meso-

subsituted −CH and −NH protons, which suggests its

oxidation and subsequent complexation with the boron center.

The pyrrolic and aromatic protons resonate at their usual

positions with a small downﬁeld shift.⁶¹¹H NMR spectra of 1

and 2 display resonances due to BODIPY protons as well as

signals associated with precursor complexes. After complexation

with [(phpy)₂Ir(μ-Cl)]₂and [{(η⁵-C₅Me₅)Ir(μ-Cl)Cl}₂], the

a triclinic system with the space group P1. The B atom lies

̅

within the dipyrrin plane and adopts the usual tetrahedral

C

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

Figure 2. UV/vis (a) and ﬂuorescence (b) spectra of L1 and complexes 1 and 2 in PBS (c, 10 μM, pH ∼ 7.4).

Figure 3. UV/vis spectra of 1 (a) and 2 (b) in PBS with increasing concentrations of CT-DNA (0−20 μM) at room temperature. Arrows show

absorbance changes with increasing CT-DNA concentration.

geometry. Angles N−B−N and F−B−F are 106.26° and

110.14°, respectively, and are comparable to those of other

related systems.⁶¹The dihedral angle between boron dipyrrin

units and the quinoline ring (C4−C5−C11−C12) is 66.00°.

Complex 1 crystallizes in the monoclinic system with the space

group C2/c, while 2 is in the triclinic system with the space

Ir−N5, 2.15 Å; Ir−Cl1, 2.38 Å] in this complex are normal and

comparable to those of other related systems.^11,12,53The N−Ir

−N and N−Ir−Cl angles are close to 90° [N3−Ir−N5, 74.29°;

N3−Ir−Cl1, 87.85°; N5−Ir−Cl1, 87.15°] (Table S1). The η⁵-

C₅Me₅ring is symmetrically bonded to the metal center with an

average Ir−C distance of 2.14 Å (range 2.12−2.16 Å). All of the

C atoms in the η⁵-C₅Me₅ring are planar, and iridium is

displaced from the centroid of the ring by 1.78 Å, which is

consistent with other reported iridium complexes.^11,12,53

Electronic Absorption Spectroscopy. UV/vis absorption

spectra of L1, 1, and 2 have been acquired in phosphate-

buﬀered saline (PBS; c, 10 μM; pH ∼ 7.4) at room temperature

(Figure 2a). Spectra of these compounds display strong low-

energy absorptions at ∼505 nm [504 nm, L1; 510 nm, 1; 514

nm, 2] and weak bands at ∼480 nm [480 nm, L1; 484 nm, 1;

488, nm 2]. These have been attributed to S0−S1 and S0−S2

transitions of the conjugated dipyrrinato ligand.^53,58,66Also,

spectra of the compounds display intense high-energy bands at

∼335 nm [335 nm, L1; 343 nm, 1; 355 nm, 2] due to

intraligand π−π* transitions.

group P1. Their pertinent view along with partial atomic

̅

numbering scheme is depicted in Figure 1, and important

geometrical parameters are summarized in Table 1.

The crystal structure of 1 showed that the [(phpy)₂Ir] unit is

coordinated with a N^N-chelating site of the BODIPY moiety,

creating a slightly distorted octahedral geometry about the Ir

metal center. The N3−Ir1−N5, N6−Ir1−C44 and N7−Ir1−

C42 bite angles in this complex are 74.3(3)°, 80.6(4)°, and

80.4(4)°, respectively. The N6 and N7 atoms from 2-

phenylpyridine are trans-disposed, which is normal and similar

to earlier reports.⁶²⁻⁶⁵The Ir1−C and Ir1−N bond distances

[Ir−C, 2.00 Å; Ir−N, 2.04 Å] and C−Ir1−N, C−Ir1−C, and

N−Ir1−N bond angles are regular and similar to other closely

related cyclometalated iridium(III) complexes.^{22,46,62,63,65}On

the other hand, Ir1 in complex 2 adopted the typical “piano-

stool” geometry, wherein the metal center coordinated with the

C₅Me₅ring in an η⁵-fashion, occupying three coordination sites.

Other sites about the metal center are occupied by the N^N-

chelating site of BODIPY via N3 and N5 atoms and a chloro

group. The Ir−N and Ir−Cl bond distances [Ir−N3, 2.08 Å;

Ligand L1 and complexes 1 and 2 are luminescent in a buﬀer

solution (PBS, pH ∼ 7.4), and all of the photophysical

experiments were performed in this system. Upon excitation at

their respective λ_exvalues (L1, 500 nm; 1, 505 nm; 2, 510 nm)

in 100% PBS (Figure 2b), these showed emission maxima at

similar positions of ∼525 nm (L1, 520 nm; 1, 525 nm; 2, 530

D

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

Figure 4. Emission spectra of EB bound to DNA in the absence (--- green line) and presence of 1 (a) and 2 (b). [EB] = 10 μM; [DNA] = 100 μM;

[1] and [2] = 0−50 μM. Arrows show changes in the emission intensity upon the addition of increasing concentrations of the complexes.

nm).⁶⁶⁻⁶⁸As a consequence of complexation, emission maxima

for 1 and 2 showed a red shift of ∼10 nm relative to ligand L1.

Electronic Absorption Titration Studies. Absorption

titration studies have been carried out (Figure 3) using a ﬁxed

concentration of 1 and 2 (10 μM) and an increasing amount of

calf-thymus DNA (CT-DNA; 0−20 μM). Usually, intercalation

or interaction of the metal complexes with base pairs of DNA

causes hypochromism with a small red/blue shift, while the

hyperchromic shift arises because of nonintercalative/electro-

static interactions.^{57,58,69−72}The extent of hypochromism gives

an idea about the strength of the intercalative binding

interaction. The band at 512 nm for 1 displays hypochromism

(35%) with a small red shift of 5 nm upon the addition of CT-

DNA, while the weak band at 278 nm shows hyperchromism

(50%) along with a red shift of 20 nm. This indicates that

interaction with the DNA results in the formation of a DNA−

drug complex, causing stabilization of the DNA du-

plex.^{53,57,58,69−72}Similarly, the gradual addition of CT-DNA

to a solution of 2 led to hypochromism (33%) for the band at

510 nm with a small red shift of 4 nm. In addition, the band due

to the intraligand charge-transfer transition at 276 nm displays

hyperchromism (37%) with a blue shift of 16 nm. The

hyperchromic eﬀect may arise because of electrostatic attraction

between a charged cation and the phosphate group of the DNA

backbone, which may cause contraction and overall damage to

the DNA secondary structure. Observed spectral changes

clearly indicated that 1 and 2 interact with DNA through

intercalation as well as groove binding via electrostatic

interactions, leading to DNA stabilization.^{53,57,58,69−72}

Ethidium Bromide (EB) Displacement Studies. To

understand the binding mode of the compounds with DNA,

competitive binding studies have been carried out between EB

(3,8-diamino-5-ethyl-6-phenylphenanthridine bromide) and 1

and 2 with CT-DNA.^74,75EB is an intercalating weakly

ﬂuorescent labeling agent often used for staining nucleic acid

and other biomolecules.^{57,58,69−72,76}After binding with DNA,

its ﬂuorescence intensity increases and displacement of EB (λ_ex,

540 nm; λ_em, 600 nm) from an EB−DNA complex by other

compounds causes quenching of intrinsic ﬂuorescence of the

EB−DNA system. This occurs because of an increase in the

concentration of free EB in solution and a lowering of the

number of binding sites accessible for EB−DNA binding.

The eﬀects of 1 and 2 on the ﬂuorescence intensity of the

EB−DNA system are shown in Figure 4. Notably, the

ﬂuorescence intensity of EB−DNA underwent an appreciable

decrease (60%, 1; 54%, 2) in the presence of 1 and 2 (50 μM)

with increasing concentrations. It has been concluded that 1

and 2 are capable of displacing EB from the EB−DNA complex

and strongly interact with DNA binding sites in the order 1 > 2.

The quenching parameters were analyzed using the Stern−

Volmer equation (Figure S7b)

I₀/I = K_q[Q] + 1

(2)

where I₀is the emission intensity in the absence of the

quencher, I is the emission intensity in the presence of the

quencher, K_qis the quenching constant, and [Q] presents the

concentration of the complex (Q = quencher). K_qvalues have

been derived from the slope of I₀/I versus [Q] plot (2.25 × 10⁴,

1; 2.08 × 10⁴, 2). Additionally, the apparent DNA binding

constants (K_app) were calculated using the equation

To compare their DNA binding aﬃnity, the intrinsic binding

constant K_bwas calculated using the equation^69,73

[DNA]/(ε_a− ε_f)/ = [DNA]/(ε_b− ε_f) + 1/k_b(ε_b− ε_f)

K_EB[EB] = K_app[complex]

(3)

(1)

where [complex] is the value at a 50% decrease of the

ﬂuorescence intensity for EB, K_EB(4.94 × 10⁵M⁻¹) is the DNA

binding constant for EB, and [EB] is the concentration of EB

(10 μM). K_appvalues were found to be 3.18 × 10⁵M⁻¹(1) and

2.64 × 10⁵M⁻¹(2). This suggests that complex 1 intercalated

rather strongly relative to 2, and this observation is in good

agreement with the conclusions drawn from UV/vis titration

studies.

where [DNA] is the concentration of DNA in base pairs, ε_ais

the apparent extinction coeﬃcient, calculated as A_obs

/

[complex], and ε_fand ε_bare to the extinction coeﬃcients of

the complex in its free and bound forms, respectively. Each set

of data upon ﬁtting in the above equation gave a straight line

with a slope of 1/(ε_b− ε_f) and a y intercept of 1/K_b(ε_b− ε_f).

K_bwas determined from the ratio of te slope to the intercept

(Figure S7a). The values of K_bvary in the order 1 (5.8 × 10⁴) >

2 (4.7 × 10⁴).

Protein Binding Studies. Fluorescence spectroscopy is

very useful in investigating the interaction and mechanism of

E

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

Figure 5. Emission spectrum of BSA (0.5 μM; λ_ex= 280 nm; λ_em= 343 nm) in the presence of increasing amounts of 1 (a) and 2 (b) (0−50 μM).

Arrows show that the emission intensity changes with increasing concentration of the complexes.

Figure 6. Synchronous spectra of BSA (black line; PBS buﬀer, c, 0.5 μM, pH ∼ 7.4) in the presence (other lines) of increasing amounts (0−50 μM)

of 1 at wavelength diﬀerences of (a) Δλ = 15 nm and (b) Δλ = 60 nm. Arrows show decreases in the emission intensity with increasing

concentrations.

binding of the compounds with bovine serum albumin

(BSA).^{35,58,77−79}For this purpose, BSA is preferred over

other proteins because of its abundance, cost eﬀectiveness, ease

of puriﬁcation, stability, and wide applications.^{35,58,77−79}It has

been established that the high ﬂuorescent nature of BSA is due

to tryptophan and tyrosine residues.^{35,58,77−79}Quenching of

the emission intensity of BSA may occur in the presence of the

complexes because of changes in the secondary structure of

protein induced by various molecular interactions.^57,80,81

Fluorescence quenching experiments on BSA in the presence

of complexes provide useful information about the structure,

dynamics, and protein folding.^{35,58,77−82}Fluorescence changes

(range 290−500 nm; λ_ex, 280 nm) in the spectrum of BSA in

the presence of varying amounts of 1 and 2 (0−50 μM) are

depicted in Figure 5. The intensity of the ﬂuorescence band for

BSA at ∼345 nm is quenched (58%, 1; 52%, 2) relative to its

initial intensity along with a small blue shift of ∼5 and 4 nm

upon the addition of 1 or 2. From observations, we concluded

that some interaction is certainly taking place between the

complexes and BSA. One can get an idea about the structural

changes and the types of quenching (static or dynamic) from

the UV/vis study (Figure S9). It is well documented that

dynamic quenching absorption spectra of ﬂuorophore do not

show a substantial change, while static quenching causes

perturbation in the absence and presence of the com-

pounds.^{35,57,77−79}

From Figure S9, it is clear that the addition of 1 and 2 to a

ﬁxed concentration of BSA leads to an increase in the intensity

(λ_abs= 220 nm), with a small blue shift indicating that these

complexes interact with the protein and follow a static

quenching mechanism. Fluorescence quenching data have

been analyzed using the Stern−Volmer (Figure S10a) and

Scatchard equations and quenching constant (K_q) evaluated

from the plot of I₀/I versus [Q]. The equilibrium binding

constant can be estimated from the Scatchard equation:

log[(I₀− I)/I] = log K_bin+ n log [Q]

(4)

where K_binis the binding constant of the compound with BSA

and n is the number of binding sites. From the log[(I₀− I)/I]

vs log [Q] plot, the number of binding sites (n) and the binding

constant (K_bin) have been calculated (Table S2). Notably,

estimated values of n for these compounds are ∼1 and strongly

suggest the presence of a single binding site in BSA for 1 and 2.

The values of K_qand K_binfor these compounds further suggest

that 1 interacts with BSA rather strongly relative to 2.

Synchronous Fluorescence Experiments. Valuable

information about the microenvironment around the ﬂuo-

rophore can be obtained from synchronous ﬂuorescence

F

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

Figure 7. 3D ﬂuorescence spectra of BSA (a) and BSA + 1 (b). [BSA] = 10⁻⁶mol L⁻¹; [1] = 10⁻⁵mol L⁻¹.

Figure 8. CD spectra of CT-DNA in the absence and presence of complexes 1(a) and 2 (b). [DNA] = 100 μM; [complex] = 0−50 μM.

spectroscopy.^35,58,83,84To investigate conformational changes

in BSA in the presence of 1 and 2, ﬂuorescence spectroscopic

experiments were carried out at Δλ = 15 and 60 nm (Δλ = λ_ex

− λ_em). A larger wavelength diﬀerence (Δλ = 60 nm) provides

information about the microenvironment for tryptophan and a

shorter one (Δλ = 15 nm) that for the tyrosine residue.^70,77,84

Emission maxima of tryptophan and tyrosine residue in

proteins depend on the polarity of its surroundings.

It has been observed that synchronous ﬂuorescence spectra

(Δλ = 15 nm) for BSA with increasing concentrations of 1 and

2 exhibit a signiﬁcant decrease in the intensity for the band at

288 nm (35.85%, 1; 31.55%, 2) without any noticeable shift

(Figures 6 and S8). On the other hand, at Δλ = 60 nm, they

showed a remarkable decrease in the ﬂuorescence intensity for

the band at 280 nm (87.42%, 1; 86.82%, 2) with small blue

shifts of 3 and 4 nm. This suggests that the ﬂuorescence

intensities for both tryptophan and tyrosine diminished with

increasing concentrations of the complexes.^{57,58,70,77,84}It

further supported that the hydrophobicity around both the

tyrosine and tryptophan residues increases and the polarity

decreases.

changes for BSA in the presence of the complexes.^57,58,85,86

Spectral changes arising for BSA in the presence of 1 and 2 are

depicted in Figures 7 and S11. Notably, the 3D spectrum of

BSA exhibits four characteristic peaks: a peak on the extreme

left, namely, peak ‘a’ assigned as the ﬁrst-order Rayleigh

scattering for which the emission wavelength matches the

excitation wavelength (λ_ex= λ_em), and the peak on the extreme

right designated as peak ‘b’ ascribed to the second-order

Rayleigh scattering for which λ_em= 2λ_ex. In addition, peak 1 is

characteristic of the tyrosine and tryptophan residues, and peak

2 is related to the polypeptide backbone and secondary

structure of the protein.^57,58,85,86

The ﬂuorescence intensity for peak 1 quenched in the

presence of complexes 1 and 2 (peak 1: 24.4%, 1; 18.0%, 2),

suggesting their binding with BSA and closeness of the binding

sites to the tryptophan and tyrosine residues. Peak 2 also

exhibited quenching (27.9%, 1; 22.2%, 2) and suggested

changes in the peptide structure of BSA. From the 3D and

synchronous ﬂuorescence spectral studies, we conclude that

interaction between BSA and 1 and 2 may be due to the

unfolding of the polypeptide and conformational changes in the

protein due to enhanced exposure to the hydrophobic region.

Circular Dichroism (CD) Spectroscopy. The conforma-

tional changes caused by 1 and 2 in CT-DNA have been

monitored by CD spectroscopic studies in a PBS buﬀer at room

temperature (Figure 8). CT-DNA itself shows bands at (−)

245 and (+) 275 nm assignable to the right-handed helicity of

Three-Dimensional (3D) Fluorescence Spectroscopy.

Excitation−emission matrix or 3D ﬂuorescence spectroscopy

provides useful information about the emission characteristics

of the ﬂuorophore by changing the excitation and emission

wavelengths simultaneously.^85,86Using this technique, one can

have an idea about the conformational and microenvironmental

G

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

B-DNA and base-pair stacking.^87,88Interaction of non-

intercalative drugs with DNA causes negligible perturbation

for the bands due to base stacking and helicity, whereas an

intercalator leads to changes in the intensity of both bands.

Further, these are sensitive toward the binding of small

molecules and a drug.^70,87−89An increase in the concentrations

of 1 and 2 led to a decrease in the intensity for both (+) and

(−) bands due to CT-DNA, which clearly indicated interaction

between the complexes and CT-DNA.

From this data, we conclude that 1 and 2 may intercalate

between neighboring base pairs of CT-DNA mainly because of

the presence of a planar aromatic dipyrrin moiety. Further, the

intensity change follows the order 1 > 2, indicating greater

eﬃcacy of 1 relative to 2 which is consistent with the UV/vis

and ﬂuorescence spectroscopic studies.

speciﬁc viscosity (η/η₀)^1/3versus [complex]/[DNA] shows

that the DNA viscosity signiﬁcantly increases with an increase

in the concentration of the complexes. On the basis of variation

in the DNA viscosity, it has been concluded that complexes

interact with CT-DNA in an intercalative mode.

Hydrolysis Study and Interaction with Nucleobases.

Hydrolysis of the M−Cl bond represents an activation step for

transition-metal anticancer complexes. M−OH₂aqua com-

plexes are typically more reactive relative to analogous chlorido

complexes.³⁵⁻⁴⁸Hydrolysis of compound 2 in 5% CD₃CN/

1

95% D₂O (v/v) was monitored by H NMR spectroscopy at

298 K (Figure S6), and acetonitrile was used to ensure the

solubility of complex 2 (the NMR spectrum of complex 2 in

DMSO shows broad features). It (c, 1 mM) underwent rapid

hydrolysis in 5% CD₃CN/95% D₂O within a minute, and the

extent of hydrolysis for this complex is 52%. To further aﬃrm

hydrolysis of the complex, NaCl (4 mol equiv) was added to

Viscosity Measurements. To understand the nature of the

interaction between 1 and 2, DNA viscosity measurements

have been carried out in the absence and presence of varying

concentrations of the complexes (Figure 9). Usually,

1

the equilibrium solution. H NMR spectra was subsequently

recorded within 10 min of the Cl⁻addition at 298 K. Signals

due to chlorido adducts enhanced in the intensity with the

addition of NaCl, while those for the aqua forms decreased,

suggesting a rapid shifting of the equilibrium toward chloride

from the aqua complex and very fast aquation.

Partition Coeﬃcient Determination. The partitioning

behavior of the drugs is usually determined by the lip-

ophilicity.^11,94−96It has been worked out by measuring the

partition coeﬃcient (log P) based on the amounts of 1 and 2

distributed in a biphasic system (n-octanol/water) using the

equation

log P = log [complex]_octanol/[complex]_water

(5)

Notably, calculated log P values (Table S3) are consistent

with earlier reports.¹⁹⁻³⁵Further, the log P value for 1 is greater

relative to complex 2, which may be related to the greater

number of hydrophobic aromatic rings in it. These results are in

keeping with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazo-

lium bromide (MTT) assay; the cytotoxicity of the complex

increases with an increase in the lipophilicity.

Figure 9. Eﬀect of increasing amounts of complexes on the relative

viscosity of CT-DNA (125 μM) in a PBS buﬀer at 25 °C in various

[complex]/[DNA] ratios.

Molecular Docking with DNA. To explore the most

feasible binding site, interaction mode, and binding aﬃnity,

molecular docking studies have been carried out on 1 and 2

using B-DNA (PDB ID: 1BNA).⁹⁷It is well-known that a

DNA−intercalator complex stabilizes via van der Waals forces,

hydrogen bonding, hydrophobic charge transfer, and electro-

static complementarities.^{35,58,76,98,99}

intercalators elongate the DNA double helix by accommodating

such molecules between the base pairs, leading to an increase in

the viscosity.^52,90,91In contrast, partial nonclassical intercalation

leads to a bending (or a kink) in the DNA helix without altering

its length and, thereby, viscosity.^92,93A plot of the relative

Figure 10. Docked model for 1 with DNA (PDB ID: 1BNA): open view (left); closed view (right).

H

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

Figure 11. (left) Docked model of 1 located within the hydrophobic pocket of HSA (PDB ID: 1h9z). (right) Interaction mode between 1 and the

polypeptide units.

The most stable binding conformation of 1 and DNA

revealed that it stacks in minor grooves via electrostatic

interactions and the complex is adjusted in such a way that a

part of the planar dipyrrin core makes the stacking interaction

favorable with DNA base pairs and ﬁts inside the DNA strands

by van der Waals forces and hydrophobic contacts (Figures 10

and S14).^27,80The resulting relative binding energies for

docked structures of 1 and 2 have been found to be −285.75

and −277.11 eV, respectively, which indicates the better

binding capability of 1 relative to 2. The results are consistent

with UV/vis and competitive EB displacement studies.

Molecular Docking with Human Serum Albumin

(HSA). To ascertain the binding mode and their location

within the protein, molecular docking studies have been

performed on complexes 1 and 2 with a protein

(HSA).^{35,57,58,100,101}HSA has been chosen over BSA for its

structural homology, and it provides more biorelevant results.

The 3D structure of crystalline albumin shows that it consists of

three structurally homologous domains: I (residues 1−195), II

(196−383), and III (384−585). Each domain has two

subdomains: A and B. Figures 11 and S15 clearly indicate

that the complexes are localized within the hydrophobic cavity

of subdomain IIA. It has been discovered that the large

hydrophobic cavity in subdomain IIA is capable of accom-

modating intercalator complexes. Amino acid residues around

the binding sites are as follows: LYS199, TRP214, PHE211,

ALA215, ARG218, LEU219, ARG257, SER287, HIS288, and

ALA291 (1); LYS195, GLN196, LEU198, LYS199, SER202,

PHE211, TRP214, ARG222, LEU238, HIS242, ARG257,

ALA291, ASP451, SER454, and LEU481 (2) (within 4 Å;

Table S4).

Density Functional Theory (DFT) Calculations. To

understand the structure and verify the geometrical parameters

(bond lengths and bond angles), geometry optimizations on 1

and 2 were carried out using the Gaussian 09 package.¹⁰²The Ir

metal center was described by the LANL2DZ basis set, and the

nonmetal atoms were described by the 6-31G** basis

set.^103−106The starting geometries were taken from the

single-crystal X-ray data and subjected to optimization.

Contour plots for the molecular orbitals were generated using

Gaussview 5.0, and the energies of the frontier molecular

orbitals for 1 and 2 were calculated. DFT calculations on 2

reproduced familiar three-legged “piano-stool” structures

(Figure S12).

From DFT calculations, it is clear that the electron densities

for both the highest occupied (HOMO) and lowest unoccupied

(LUMO) molecular orbitals are localized mainly on the

dipyrrin core of BODIPY and lack any electronic communi-

cation with the metal center (Figure S13). Calculated HOMO

energies for the complexes are in the order 1 (−5.95 eV) > 2

(−6.07 eV), and those for the LUMO are 1 (−2.94 eV) > 2

(−3.02 eV). The diﬀerences between the HOMO and LUMO

in 1 (−3.01 eV) and 2 (−3.04 eV) are almost identical. The

higher HOMO energies for 1 relative to 2 are responsible for

the better intercalative interaction between DNA base pairs and

complex 1.⁶⁹The results are in good agreement with the

experimental data, and factors like the lipophilicity, hydrogen

bonding, steric bulk, rotational motion, etc., can also aﬀect their

biological activity.

Eﬀect of L1, 1, and 2 on the Viability and Proliferation

of the HeLa and Human Embryonic Kidney (HEK293)

Cells. MTT assay has been performed to determine the

cytotoxicity of ligand L1 and complexes 1 and 2 in the

concentration range of 20−100 μM.¹⁰⁷

As depicted in Figure 12, L1 displays marginal toxicity at

relatively high concentrations (100 μM) after up to 24 h of

treatment because more than 85% cells were found alive. On

the other hand, 1 and 2 show relatively high toxicity, where

approximately 26% and 29% cells were found alive. The

estimated IC₅₀values for 1 and 2 turned out to be 32.4 and

51.9 μM, respectively, which are comparable to that of cisplatin

Docking studies further revealed the occurrence of various

electrostatic and hydrogen-bonding interactions between the

complexes and HSA. These interactions play a major role in

lowering the hydrophilicity and enhancing the hydrophobicity

of HSA and thereby stabilizing the complex·HSA system. The

binding energies for the complexes with HSA are found to be

−378.11 eV (1) and −321.58 eV (2) (Figures 11 and S15).

The results also provided structural evidence for the distinct

optical response of BSA in the presence of complexes 1 and 2.

I

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

L1, 1, and 2 enter the cell membrane and show signiﬁcant

intracellular ﬂuorescence. A closer observation revealed that L1

and 1 show distinct ﬂuorescence in the extranuclear region with

a clear demarcation of the nuclear membrane, while 2

distributed unevenly throughout the cell. Moreover, major

diﬀerences were not observed between the BODIPY ligand and

its metal derivatives, implying that uptake and distribution

characteristics of the compounds are mainly determined by the

BODIPY moiety.

CONCLUSION

■

In summary, through this work, two iridium(III) complexes

containing a BODIPY ligand have been synthesized and

thoroughly characterized by various techniques. It has been

clearly shown that these eﬃciently interact with DNA in an

intercalative mode. From the molecular docking studies, it has

been established that 1 and 2 bind with DNA in its minor

groove via intercalative interactions but with protein via

hydrophobic residues located within the subdomain IIA cavity.

Indeed, the ﬂuorescence characteristics of the ligand and

complexes allowed monitoring of their in vitro uptake in cancer

cells. These exhibited signiﬁcant cytotoxicity toward the HeLa

cell line and showed a preference for accumulation in cell

membranes without reaching the nuclei. Moreover, it is

apparent that the BODIPY moiety solely determines the

cellular uptake and ﬂuorescence staining pattern of the ligand

and complexes. Among these, 1 displayed the lowest IC₅₀value

and distinct changes in the nuclear morphology, with

fragmented nuclei on the cell surface indicating apoptotic cell

death. Correlation analysis showed that an increase in the

hydrophobicity of 1 causes an increase in cellular accumulation,

which generally results in an increase in the potency. The

results shown here will be helpful in understanding the

interaction of iridium complexes with DNA and proteins.

Importantly, it also highlights that inclusion of 2-phenylpyridine

along with N^N-donor ligand can create complexes with

enhanced potency and thereby provide a new strategy beneﬁcial

for the development of these types of complexes.

Figure 12. Cytotoxicity proﬁle of L1, 1, and 2 against the HeLa cell

line.

(the calculated IC₅₀value under analogous conditions was

found to be 21.6 μM). Further, to evaluate the selectivity of 1

and 2 toward cancer cells, a cytotoxicity experiment was also

carried out against normal cell lines, HEK293. As shown in

Figure S17, 1 and 2 show less toxicity toward HEK293 cells

than HeLa cells. The estimated IC₅₀values for 1 and 2 turned

out to be 85.5 and 100 μM, respectively. Under similar

conditions, cisplatin showed IC₅₀of 80.1 μM, indicating the

selectivity of 1 and 2 toward cancer cells is comparable to that

of cisplatin. In summary, 1 elicited a maximum toxicity

response, followed by 2 for both cell lines.

Change in the Nuclear Morphology and Apoptosis

Induction. The nuclear morphology is a powerful indicator of

cellular health and apoptotic conditions; hence, changes in the

nuclear morphology following treatment with 1 and 2 have

been examined by Hoechst 33342 staining.^69,108,109Changes in

the nuclear morphology, chromatin condensation, and

fragmented nuclei are a few characteristics of apoptotic cells.

As shown in Figure 13, the cells treated with 1 and 2 show

uneven nuclear staining, and abnormal nuclear morphology

along with condensed chromatin, as shown by bright spots

within the nuclei. This clearly indicates apoptotic eﬃcacy of 1

and 2, leading to cancer cell death.

EXPERIMENTAL SECTION

■

Reagents. Standard literature procedures have been employed for

drying and distilling the solvents prior to their use.¹¹⁰Hydrated

iridium(III) chloride, 2-phenylpyridine, pentamethylcyclopentadiene,

2,3-dicloro-5,6-dicyano-1,4-benzoquinone (DDQ), pyrrole, triﬂuoro-

acetic acid, anisidine, triethylamine, and boron triﬂuoride diethyl

etherate were procured from Sigma-Aldrich India and used as received

without further puriﬁcation. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphe-

nyltetrazolium bromide (MTT) and ethidium bromide (EB) were

In Vitro Confocal Microscopic Experiments. The

detection of L1 and complexes 1 and 2 in living cells has

also been explored by ﬂuorescence microscopy. The complexes

were incubated with HeLa cells for 2 h at 37 °C and visualized

by a confocal ﬂuorescence microscope. As shown in Figure 14,

Figure 13. Nuclear morphology using Hoechst staining following treatment with 1 and 2 (scale bar: 20 μm).

J

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

Figure 14. Cellular uptake of L1, 1, and 2 by HeLa cell lines (scale bar: 20 μm).

purchased from Hi-Media Laboratories and Loba Chemie, respec-

tively. Calf-thymus DNA (CT-DNA) was acquired from Bangalore

Genei. Human cervical cancer (HeLa) and human embryonic kidney

(HEK293) cell lines were obtained from National Centre for Cell

Science, Pune, India. Other common reagents of highest purity were

purchased from local ﬁrms.

calculated and reﬁned using the SHELX riding model.^111,112The

computer program PLATON was used for analysis of the interaction

and stacking distances.^112−114Disordered solvent molecules were

removed by the SQUEEZE command in PLATON.^112−114CCDC

1553126 (L1), 1553128 (1), and 1553125 (2) contain the

supplementary crystallographic data for this paper.

General Methods. Elemental analyses for C, H, and N were

obtained on an Elementar Vario EL III Carlo Erba 1108 elemental

analyzer. Electronic absorption and ﬂuorescence spectra were acquired

on Shimadzu UV-1601 and PerkinElmer LS 55 ﬂuorescence

Partition Coeﬃcient Determination. The lipophilicities of 1 and

2 have been determined by the “shake-ﬂask” method using octanol/

water phase partitions. Octanol-saturated water and water-saturated

octanol were prepared using analytical-grade octanol and double-

distilled water. The complexes under study (1 mg mL⁻¹; 1:6 ethanol/

water) were diluted to 2, 4, 6, 8, and 10 μg mL⁻¹in water;

subsequently, these (1 mg mL⁻¹) were diluted to 2, 4, 6, 8, and 10 μg

mL⁻¹in octanol. Appropriate amounts of the complexes (4 mg mL⁻¹)

were shaken for 24 h at room temperature in equal volume (50:50).

After equilibrium, the organic and aqueous phases were separated and

centrifuged. Finally, the concentration of the drug in each phase was

determined by UV/vis spectroscopy. The sample solution concen-

tration was used to calculate log P and the partition coeﬃcients for 1

and 2 using the equation log P = log [complex]_octanol/[complex]_water

Far-UV CD Spectroscopy. CD spectra were recorded on a Jasco J-

815 spectropolarimeter at 25 °C using a quartz cell (0.1 cm path

length) and scanned in the spectral range 220−300 nm. The

concentration of CT-DNA (50 μM) was held constant and those

for complexes 1 and 2 varied from 10 to 50 μM. The ﬁnal spectra were

taken as the average of two accumulated runs.

1

spectrometers, respectively. H and ¹³C NMR spectra were acquired

on a JEOL AL 500/300 FT-NMR spectrometer using tetramethylsi-

lane [Si(CH₃)₄] as an internal reference. Electrospray ionization mass

spectrometry (ESI-MS) measurements were made on a Bruker

Daltonics Amazon SL ion-trap mass spectrometer. After dissolution

of the samples in 100% acetonitrile with 0.1% formic acid, these were

introduced into the ESI source through a syringe pump at a ﬂow rate

of 100 mL h⁻¹. The capillary voltage was 4500 V and dry gas ﬂow 8 L

min⁻¹with the dry gas at 300 °C. An MS scan was acquired for 2.0

min, and spectral printouts were averaged over each scan.

Fluorescence microscopic images were taken on a EVOS FL cell

imaging system.

X-ray Structure Determination. Crystals suitable for single-

crystal X-ray analyses for L1 and complexes 1 and 2 were obtained by

the slow diﬀusion of hexane over a dichloromethane solution of the

respective compounds. X-ray data were collected on a dual-source

Supernova CCD system from Agilent Technologies (Oxford

Diﬀraction) at room temperature with Mo Kα radiation (λ =

0.71073 Å). Structures were solved by direct methods (SHELXS-97)

and reﬁned by full-matrix least squares on F²(SHELX-97). All of the

non-H atoms were treated anisotropically, and H atoms attached to C

atoms were included as a ﬁxed contribution and geometrically

Viscosity Measurements. Viscosity measurements were made

using an Ubbelodhe viscometer immersed in a constant-temperature

bath at 25 °C. Data are presented as η/η₀versus [complex]/[DNA],

where η is the speciﬁc viscosity of DNA in the presence of complexes

and η₀is the speciﬁc viscosity of DNA alone in a PBS buﬀer. Speciﬁc

K

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

viscosity values have been calculated from the observed ﬂow time of a

DNA solution (t) corrected for the buﬀer alone (t₀), η = (t − t₀)/t₀.

Molecular Docking. Molecular docking studies on 1 and 2 have

been performed using HEX 6.1 software and Q-SiteFinder, an

interactive molecular graphics program for interaction and docking

calculations and to classify the possible binding sites of biomolecules.⁹⁸

DFT calculations have been carried out using Gaussian 09 by the

B3LYP method.¹⁰²The geometries of the compounds have been

optimized using a standard 6-31G** basis set for C, H, N, O, B, F, P,

and Cl, while LANL2DZ was used for Ir with the eﬀective core

pseudopotential for the metal.^103−106Coordinates for metal complexes

have been taken from their optimized structures as a .mol ﬁle and

transformed to PDB using CHIMERA 1.5.1 software. The crystal

structure of B-DNA (PDB ID: 1BNA) has been taken from the

protein data bank (http://www.rcsb.org./pdb). Visualization of the

docked molecules has been made by Discovery Studio 3.5 software. The

default parameters have been used for docking calculations with the

correlation-type shape only, FFT mode at the 3D level, and grid

dimension 6 with receptor range 180 and ligand range 180 with twist

range 360 and distance range 40.

Synthesis of 5-[6-Methoxy-2-(1H-pyrazol-1-yl)quinoline]-

dipyrromethane (B). Pyrrole (10.0 mL) and catalytic amounts of

triﬂuoroacetic acid (3 drops) were added to a ﬂask containing

aldehyde A (1.5 g, 5.9 mmol) and the contents of the ﬂask stirred at

room temperature for 24 h. After completion of the reaction

[monitored by thin-layer chromatography (TLC)], the ensuing

solution was concentrated to dryness under reduced pressure. The

crude product thus obtained was puriﬁed by column chromatography

(SiO₂; ethyl acetate/hexane). Yield: 1.63 g, 75%. Anal. Calcd for

C₂₂H₁₉N₅O: C, 71.53; H, 5.18; N, 18.96. Found: C, 71.46; H, 5.12; N,

18.90. ¹H NMR (CDCl₃, 300 MHz): δ3.87 (s, 3H, O methyl), 5.89 (s,

2H, pyrrolic H), 6.11 (s, 2H, pyrrolic H), 6.29 (s, 1H, meso-H), 6.46

(s, 1H, pyrazole H), 6.70 (s, 2H, pyrrolic H), 6.99 (s, 1H, pyrazole H),

7.33 (d, 1H, J = 9.0 Hz, pyrazole H), 7.79 (s, 1H, aromatic H), 7.88 (d,

1H, J = 9.0 Hz, aromatic H), 8.15 (s, 1H, aromatic H), 8.19 (s, 1H,

aromatic H), 9.07 (br, 2H, pyrrolic N−H). ¹³C NMR (CDCl₃, 75

MHz): δ37.6, 55.5, 104.6, 106.4, 106.9, 108.0, 117.3, 123.3, 128.3,

128.9, 130.2, 131.0, 131.1, 132.5, 139.1, 140.7, 141.1, 141.6, 147.1,

158.1. IR (KBr pellets, cm⁻¹): 3412, 3349, 2925, 1595, 1557, 1494,

1448, 1392, 1348, 1281, 1116, 1095, 1041, 940, 778, 768.

Synthesis of L1. DDQ (0.62 g, 2.7 mmol) dissolved in benzene

(50.0 mL) was added dropwise to a solution of B (1.0 g, 2.70 mmol)

in dichloromethane (15.0 mL) under stirring for 4 h. The reaction

mixture was stirred for an additional 2 h. After completion of the

reaction, the contents of the ﬂask was concentrated to dryness under

reduced pressure. The crude product was dissolved in dichloro-

methane and ﬁltered to remove any solid impurities. Triethylamine

(1.5 mL) and BF₃·Et₂O (3.0 mL) were successively added to this

solution, and the reaction mixture was stirred for 15 min at room

temperature. The progress of the reaction was monitored by TLC.

After completion of reaction, it was ﬁltered and the ﬁltrate washed

three times with water, extracted with dichloromethane, and

concentrated to dryness under reduced pressure. The crude product

thus obtained was charged on a ﬂash column (SiO₂; CH₂Cl₂/hexane).

The dark-orange-red band was collected and concentrated to dryness

to aﬀord the desired product. Yield: 0.34 g, 30%. Anal. Calcd for

C₂₂H₁₆BF₂N₅O: C, 63.64; H, 3.88; N, 16.87. Found C, 63.58; H, 3.82;

Preparation of the Stock Solutions of Ligands and Their

Complexes. The complexes were dissolved in DMSO (c, 100 mM)

and further diluted in a complete Dulbecco’s modiﬁed Eagle’s medium

[DMEM; culture medium consisting of 10% fetal bovine serum

(FBS)]. The maximum concentration of DMSO even at the highest

level of the drugs was less than 0.1% v/v.

Cytotoxicity and Proliferation Assay by MTT Assay. The

cytotoxic impacts of L1, 1, and 2 have been explored using the HeLa

and HEK293 cells by performing MTT assay.¹⁰⁷In a typical

procedure, the HeLa cells were seeded in a 96-well plate using

minimum essential media (MEM; Himedia) containing 10% FBS and

1% penicillin streptomycin and incubated at 37 °C under a humidiﬁed

CO₂(5%) environment for 24 h. The cells were treated with L1, 1.

and 2 in the concentration range of 20−100 μM for a period of 24 h.

Subsequently, media were removed and the cells treated with 0.5 mg

mL⁻¹MTT in MEM over a period of an additional 4 h. Later, the

MTT-containing media were removed, and 100 μL of DMSO was

added to each well. After 15 min of incubation, the plate was read

under a Biotek plate reader at 540 nm. The experiment was performed

in triplicate. The cytotoxicity against the HEK293 cells was performed

by the same protocol using DMEM. The cell viability was calculated

using absorbance at 540 nm.

1

N, 16.82. H NMR (CDCl₃, 500 MHz, a few drops of DMSO-d₆): δ

3.96 (s, 3H, methoxy), 6.31 (d, 1H, J = 1.5 Hz, aromatic H), 6.41 (d,

2H, J = 3.0 Hz, pyrrolic H), 6.69 (d, 2H, J = 3.5 Hz, pyrrolic H), 7.15

(d, 1H, J = 3.0 Hz, aromatic H), 7.44 (s, 1H, J = 2.0 Hz, aromatic H),

7.52 (m, 1H, aromatic H), 7.88 (s, 2H, pyrrolic H), 8.04 (d, 1H, J =

10.0 Hz, aromatic H), 8.24 (s, 1H, aromatic H), 8.36 (d, 1H, J = 3.0

Hz, aromatic H). ¹³C NMR (CDCl₃, 125 MHz, a few drops of DMSO-

d₆): δ 55.8, 105.2, 107.9, 118.5, 120.5, 125.0, 126.8, 129.5, 130.2,

135.4, 140.5, 142.1, 143.0, 144.0, 144.6, 158.7. IR (KBr pellets, cm⁻¹):

3106, 2929, 1592, 1557, 1487, 1411, 1387, 1357, 1257, 1140, 1108,

975, 764. ESI-MS. Calcd for (M + Na)⁺: m/z 438.1314. Found: m/z

438.1351.

%cell viability = [mean o.d. of the treated cell/mean o.d. of the

control] × 100

Bioimaging Studies. The cellular uptake for L1, 1, and 2 has been

investigated by confocal laser scanning microscopy. HeLa cells were

seeded in 27 mm confocal dishes and incubated for 24 h. Further, the

cells were treated with L1, 1, and 2 for a period of 4 h and

subsequently washed one time with PBS. The intracellular

ﬂuorescence was studied using an excitation laser (515 nm) and

emission recorded in the range 525−600 nm.

Synthesis. Synthesis of 6-Methoxy-2-(1H-pyrazol-1-yl)quinoline-

3-carbaldehyde (A). A was prepared by reacting 2-chloro-6-

methoxyquinoline-3-carbaldehyde (2.21 g, 10 mmol) with 1H-pyrazole

(1.02 g, 15 mmol) in toluene (25 mL) and heating under reﬂuxing

conditions with continuous stirring for 48 h. After cooling, the reaction

mixture was treated with a saturated NaHCO₃solution and extracted

with CH₂Cl₂(100 mL × 2). The organic layer was separated, dried,

and concentrated to dryness under reduced pressure. The crude

product thus obtained was puriﬁed by column chromatography (SiO₂;

ethyl acetate/hexane; 2.02 g, 80%). Anal. Calcd for C₁₄H₁₁N₃O₂: C,

66.40; H, 4.38; N, 16.59. Found: C, 66.35; H, 4.34; N, 16.55. ¹H NMR

(CDCl₃): δ 3.93 (s, 3H, OCH₃), 6.56 (s, 1H), 7.24 (d, 2H, J = 7.2

Hz), 7.48 (d, 1H, J = 6.9 Hz), 7.82 (s, 1H), 7.94 (d, 1H, J = 8.7 Hz),

8.65 (s, 2H), 10.67 (s, 1H), 11.25 (s, 1H). IR (KBr pellets, cm⁻¹):

3043, 2872, 1688, 1661, 1614, 1579, 1490, 1455, 1369, 1333, 1165,

1132, 1046, 940, 807, 761, 749.

Synthesis of 1. The dimeric complex [(phpy)₂Ir(μ-Cl)]₂(0.12 g,

0.1 mmol) was added to a suspension of L1 (0.10 g, 0.24 mmol) in 1:1

CH₂Cl₂/MeOH (50.0 mL) and reaction mixture stirred for 12 h at

room temperature. After ﬁltration to remove any solid impurities, a

methanolic solution of NH₄PF₆(0.040 g, 0.25 mmol, 10 mL) was

added to it and the resulting mixture stirred for 4 h. The volume of the

solution was reduced to half under reduced pressure and precipitated

using diethyl ether. The resulting solid was ﬁltered and washed twice

with diethyl ether. Yield: 75% (0.16 g). Anal. Calcd for

C₄₄H₃₂BF₈IrN₇OP: C, 49.82; H, 3.04; N, 9.24. Found: C, 49.75; H,

1

3.10; N, 9.18. H NMR (CDCl₃, 500 MHz): δ 3.90 (s, 3H, OCH₃),

6.05 (d, 1H, J = 7.5 Hz, aromatic H), 6.42 (d, 2H, J = 4.5 Hz, aromatic

H), 6.45 (d, 1H, J = 3.0 Hz, aromatic H), 6.52 (s, 1H, aromatic H),

6.70 (s, 1H, aromatic H), 6.81 (s, 1H, aromatic H), 6.98−7.07 (m, 6H,

aromatic H), 7.24 (d, 2H, J = 3.0 Hz, aromatic H), 7.29 (s, 1H,

aromatic H), 7.40 (d, 1H, J = 4.5 Hz, aromatic H), 7.61−7.66 (m, 3H,

aromatic H), 7.81 (d, 1H, J = 10.5 Hz, aromatic H), 7.88 (s, 1H,

aromatic H), 7.94 (s, 1H, aromatic H), 7.98 (s, 1H, aromatic H), 8.12

(t, 2H, J = 6.5 Hz, aromatic H), 8.22 (d, 1H, J = 6.5 Hz, aromatic H),

8.26 (s, 1H, aromatic H), 8.50 (s, 1H, aromatic H).¹³C NMR (CDCl₃,

125 MHz): δ 56.1 (OCH₃), 106.6, 112.0, 119.8, 122.8, 123.2, 124.1,

L

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

124.5, 125.3, 127.0, 130.0, 130.5, 130.7, 131.2, 132.0, 134.3, 138.5,

143.1, 144.1, 146.3, 148.5, 150.6 (C₆H₆). ESI-MS. Calcd for [M −

PF₆]⁺: m/z 937.1210. Found: m/z 937.1000.

(2) Romero-Canelon

́

, I.; Sadler, P. J. Next-Generation Metal

Anticancer Complexes: Multitargeting via Redox Modulation. Inorg.

Chem. 2013, 52, 12276−12291.

Synthesis of 2. 2 was prepared following the above procedure for 1

using [{(η⁵-C₅Me₅)Ir(μ-Cl)Cl}₂] (0.08 g, 0.1 mmol) in place of

[(phpy)₂Ir(μ-Cl)]₂. It was isolated as a red precipitate in good yield.

Yield: 73% (0.075 mg). Anal. Calcd for C₃₂H₃₁BClF₈IrN₅OP: C,

(3) Vanrijt, S. H.; Sadler, P. J. Current applications and future

potentials for bioinorganic chemistry in the developement of anticancr

drugs. Drug Discovery Today 2009, 14, 1089−1097.

(4) Suss-Fink, G. Areneruthenium complexes as anticancer agents.

̈

1

41.64; H, 3.38; N, 7.58. Found: C, 41.58; H, 3.45; N, 7.52. H NMR

Dalton Trans. 2010, 39, 1673−1688.

(CDCl₃, 500 MHz): δ 1.59 (s, 15H, methyl), 4.03 (s, 3H, methoxy),

6.54 (d, 1H, J = 4.0 Hz, aromatic H), 6.67 (d, 2H, J = 4.0 Hz, pyrrolic

H), 6.71 (m, 2H, pyrrolic H), 7.03 (d, 1H, J = 4.0 Hz, aromatic H),

7.35 (d, 1H, J = 3.0 Hz, aromatic H), 7.65 (m, 1H, aromatic H), 7.94

(d, 1H, J = 2.0 Hz, aromatic H), 8.05 (d, 2H, J = 4.0 Hz, pyrrolic H),

8.39 (d, 1H, J = 9.5 Hz, aromatic H), 8.51 (s, 1H, aromatic H). ¹³C

NMR (CDCl₃, 125 MHz): δ56.4, 90.4, 106.8, 112.5, 115.9, 120.3,

121.8, 127.5, 128.8, 130.3, 131.4, 132.1, 134.6, 141.0, 143.9, 146.8,

148.6, 160.4. ESI-MS. Calcd for [M − PF₆]⁺: m/z 778.1. Found: m/z

778.2.

(5) Gasser, G.; Ott, I.; Metzler-Nolte, N. Organometallic Anticancer

Compounds. J. Med. Chem. 2011, 54, 3−25.

(6) Noffke, A. L.; Habtemariam, A.; Pizarro, A. M.; Sadler, P. J.

Designing organometallic compounds for catalysis and therapy. Chem.

Commun. 2012, 48, 5219−5246.

(7) Argyriou, A. A.; Polychronopoulos, P.; Iconomou, G.; Chroni, E.;

Kalofonos, H. P. A review on oxaliplatin-induced peripheral nerve

damage. Cancer Treat. Rev. 2008, 34, 368−377.

(8) Johnstone, T. C.; Wilson, J. J.; Lippard, S. J. Monofunctional and

Higher-Valent Platinum Anticancer Agents. Inorg. Chem. 2013, 52,

12234−12249.

(9) Cepeda, V.; Fuertes, M. A.; Castilla, J.; Alonso, C.; Quevedo, C.;

Perez, J. M. Biochemical mechanisms of cisplatin cytotoxicity. Anti-

Cancer Agents Med. Chem. 2007, 7, 3−18.

(10) Novohradsky, V.; Liu, Z.; Vojtiskova, M.; Sadler, P. J.; Brabec,

V.; Kasparkova, J. Mechanism of cellular accumulation of an

iridium(III) pentamethylcyclopentadienyl anticancer complex contain-

ing a C,N-chelating ligand. Metallomics 2014, 6, 682−690.

(11) Liu, Z.; Habtemariam, A.; Pizarro, A. M.; Fletcher, S. A.; Kisova,

A.; Vrana, O.; Salassa, L.; Bruijnincx, P. C. A.; Clarkson, G. J.; Brabec,

V.; Sadler, P. J. Organometallic Half-sandwich Iridium Anticancer

Complexes. J. Med. Chem. 2011, 54, 3011−3026.

(12) Almodares, Z.; Lucas, S. J.; Crossley, B. D.; Basri, A. M.; Pask, C.

M.; Hebden, A. J.; Phillips, R. M.; McGowan, P. C. Rhodium, Iridium,

and Ruthenium Half-Sandwich Picolinamide Complexes as Anticancer

Agents. Inorg. Chem. 2014, 53, 727−736.

(13) Peacock, A. F. A.; Sadler, P. J. Medicinal Organometallic

Chemistry: Designing Metal Arene Complexes as Anticancer Agents.

Chem. - Asian J. 2008, 3, 1890−1899.

ASSOCIATED CONTENT

■

S

* Supporting Information

The Supporting Information is available free of charge on the

ACS Publications website at DOI: 10.1021/acs.inorg-

chem.7b01693.

¹H and ¹³C NMR and ESI-MS spectra, UV/vis titration

curves, ﬂuorescence spectra, theoretical studies, and

tables (PDF)

Accession Codes

CCDC 1553125−1553126 and 1553128 contain the supple-

mentary crystallographic data for this paper. These data can be

obtained free of charge via www.ccdc.cam.ac.uk/data_request/

cif, or by emailing data_request@ccdc.cam.ac.uk, or by

contacting The Cambridge Crystallographic Data Centre, 12

Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

(14) Yellol, G. S.; Donaire, A.; Yellol, J. G.; Vasylyeva, V.; Janiak, C.;

Ruiz, J. On the antitumor properties of novel cyclometalated

benzimidazole Ru(II), Ir(III) and Rh(III) complexes. Chem. Commun.

2013, 49, 11533−11535.

(15) Geldmacher, Y.; Oleszak, M.; Sheldrick, W. S. Rhodium(III) and

iridium(III) complexes as anticancer agents. Inorg. Chim. Acta 2012,

393, 84−102.

(16) Chellan, P.; Land, K. M.; Shokar, A.; Au, A.; An, S. H.; Taylor,

D.; Smith, P. J.; Riedel, T.; Dyson, P. J.; Chibale, K.; Smith, G. S.

Synthesis and evaluation of new polynuclear organometallic Ru(II),

Rh(III) and Ir(III) pyridyl ester complexes as in vitro antiparasitic and

antitumor agents. Dalton Trans. 2014, 43, 513−526.

AUTHOR INFORMATION

■

Corresponding Author

*E-mail: dspbhu@bhu.ac.in. Tel.: +91 542 6702480.

ORCID

Shaikh M. Mobin: 0000-0003-1940-3822

Daya Shankar Pandey: 0000-0002-6576-4234

Notes

The authors declare no competing ﬁnancial interest.

(17) Sava, G.; Zorzet, S.; Perissin, L.; Mestroni, G.; Zassinovich, G.;

Bontempi, A. Antineoplastic Activity of Planar Rhodium(I) Complexes

in Mice Bearing Lewis Lung Carcinoma and P388 Leukemia. Inorg.

Chim. Acta 1987, 137, 69−71.

(18) Giraldi, T.; Sava, G.; Mestroni, G.; Zassinovich, G.; Stolfa, D.

Antitumour Action of Rhodium (I) and Iridium (I) Complexes.

Chem.-Biol. Interact. 1978, 22, 231−238.

(19) He, L.; Li, Yi.; Tan, C. P.; Ye, R. R.; Chen, M. H.; Cao, J. J.; Ji, L.

N.; Mao, Z. W. Cyclometalated Iridium(III) Complexes as Lysosome-

targeted Photodynamic Anticancer and Real-time Tracking Agents.

Chem. Sci. 2015, 6, 5409−5418.

(20) Kumar, A.; Kumar, A.; Gupta, R. K.; Paitandi, R. P.; Singh, K. B.;

Trigun, S. K.; Hundal, M. S.; Pandey, D. S. Cationic Ru(II), Rh(III)

and Ir(III) Complexes Containing Cyclic π-perimeter and 2-

Aminophenyl Benzimidazole Ligands: Synthesis, Molecular Structure,

DNA and Protein Binding, Cytotoxicity and Anticancer Activity. J.

Organomet. Chem. 2016, 801, 68−79.

(21) Farrer, N. J.; Woods, J. A.; Salassa, L.; Zhao, Y.; Robinson, K. S.;

Clarkson, G.; Mackay, F. S.; Sadler, P. J. Angew. Chem., Int. Ed. 2010,

49, 8905−8908.

ACKNOWLEDGMENTS

■

We thankfully acknowledge the Council of Scientiﬁc and

Industrial Research, New Delhi, India, for providing ﬁnancial

support through the Scheme 01(2791)/14/EMR-II and also for

the award of a Senior Research Fellowship to R.P.P. (Award

09/013(0514)/2013-EMR-I). We are thankful to the Head,

Department of Chemistry, Institute of Science, Banaras Hindu

University, Varanasi, Uttar Pradesh, India, for extending its

laboratory facilities. S.M.M. acknowledges SIC, Indian Institute

of Technology Indore, Indore, India, for its confocal facility and

SERB, DST, for a research grant. V.S. acknowledge UGC for a

research fellowship.

REFERENCES

■

(1) Hartinger, C. G.; Metzler-Nolte, N.; Dyson, P. J. Challenges and

Opportunities in the Development of Organometallic Anticancer

Drugs. Organometallics 2012, 31, 5677−5685.

M

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

(22) Tripathy, S. K.; De, U.; Dehury, N.; Pal, S.; Kim, H. S.; Patra, S.

Dinuclear[[{(p-cym)RuCl}₂(μ-phpy)](PF₆)₂and heterodinuclear

[(ppy)₂Ir(μ-phpy)Ru(p-cym)Cl](PF₆)₂complexes: synthesis, struc-

ture and anticancer activity. Dalton Trans. 2014, 43, 14546−14549.

(23) Ye, R. R.; Tan, C. P.; Ji, L. N.; Mao, Z. W. Coumarin-appended

Phosphorescent Cyclometalated Iridium(III) Complexes as Mitochon-

dria-targeted Theranostic Anticancer Agents. Dalton Trans. 2016, 45,

13042−13051.

(24) Ye, R. R.; Tan, C. P.; He, L.; Chen, M. H.; Ji, L. N.; Mao, Z. W.

Cyclometalated Ir(III) complexes as targeted theranostic anticancer

therapeutics: combining HDAC inhibition with photodynamic

therapy. Chem. Commun. 2014, 50, 10945−10948.

(39) Liu, Z.; Sadler, P. J. Organoiridium Complexes: Anticancer

Agents and Catalysts. Acc. Chem. Res. 2014, 47, 1174−1185.

(40) Ruiz, J.; Vicente, C.; de Haro, C.; Bautista, D. Novel Bis-C,N-

cyclometalated Iridium(III) Thiosemicarbazide Antitumor Complexes:

Interactions with Human Serum Albumin and DNA, and Inhibition of

Cathepsin B. Inorg. Chem. 2013, 52, 974−982.

(41) Gupta, G.; Das, A.; Ghate, N. B.; Kim, T.; Ryu, J. Y.; Lee, J.;

Mandal, N.; Lee, C. Y. Novel BODIPY-based Ru(II) and Ir(III)

metallarectangles: cellular localization of compounds and their

antiproliferative activities. Chem. Commun. 2016, 52, 4274−4277.

(42) Hisamatsu, Y.; Shibuya, A.; Suzuki, N.; Suzuki, T.; Abe, R.; Aoki,

S. Design and Synthesis of Amphiphilic and Luminescent Tris-

Cyclometalated Iridium(III) Complexes Containing Cationic Peptides

as Inducers and Detectors of Cell Death via a Calcium-Dependent

Pathway. Bioconjugate Chem. 2015, 26, 857−879.

(25) Yang, C.; Mehmood, F.; Lam, T. L.; Chan, S. L. F.; Wu, Y.;

Yeung, C. S.; Guan, X.; Li, K.; Chung, C. Y. S.; Zhou, C. Y.; Zou, T.;

Che, C. M. Stable luminescent iridium(III) complexes with bis(N-

heterocyclic carbene) ligands: photo-stability, excited state properties,

visible-light-driven radical cyclization and CO₂reduction, and cellular

imaging. Chem. Sci. 2016, 7, 3123−3136.

́

(43) Liu, Z.; Romero-Canelon, R. I.; Qamar, B.; Hearn, J. M.;

Habtemariam, A.; Barry, N. P. E.; Pizarro, A. M.; Clarkson, G. J.;

Sadler, P. J. The Potent Oxidant Anticancer Activity of Organoiridium

Catalysts. Angew. Chem. 2014, 126, 4022−4027.

(26) Zimbron, J. M.; Passador, K.; Gatin-Fraudet, B.; Bachelet, C. M.;

Plazuk, D.; Chamoreau, L. M.; Botuha, C.; Thorimbert, S.; Salmain, M.

(44) Li, S. P. Y.; Lau, C. T. S.; Louie, M. W.; Lam, Y. W.; Cheng, S.

H.; Lo, K. K. W. Mitochondria-targeting cyclometalated iridium(III)-

PEG complexes with tunable photodynamic activity. Biomaterials

2013, 34, 7519−7532.

̇

Synthesis, Photophysical Properties, and Living Cell Imaging of

Theranostic Half-Sandwich Iridium−4,4-Difluoro-4-bora-3a,4a-diaza-s-

indacene (BODIPY) Dyads. Organometallics 2017, 36, 3435.

(27) Chi, Y.; Chou, P. T. Transition-metal phosphors with

cyclometalating ligands: fundamentals and applications. Chem. Soc.

Rev. 2010, 39, 638−655.

́

(45) Liu, Z.; Romero-Canelon, I.; Habtemariam, A.; Clarkson, G. J.;

Sadler, P. J. Potent Half-Sandwich Iridium(III) Anticancer Complexes

Containing C^N-Chelated and Pyridine Ligands. Organometallics

2014, 33, 5324−5333.

(28) Lowry, M. S.; Bernhard, S. Synthetically Tailored Excited States:

Phosphorescent, Cyclometalated Iridium(III) Complexes and Their

Applications. Chem. - Eur. J. 2006, 12, 7970−7977.

(29) Majumdar, P.; Yuan, X.; Li, S.; Le Guennic, B.; Ma, J.; Zhang,

C.; Jacquemin, D.; Zhao, J. Cyclometalated Ir(III) complexes with

styrylBODIPY ligands showing near IR absorption/emission: prep-

aration, study of photophysical properties and application as

photodynamic/luminescence imaging materials. J. Mater. Chem. B

2014, 2, 2838−2854.

(30) Lo, K. K.; Zhang, K. Y.; Leung, S. K.; Tang, M. C. Exploitation

of the Dual-Emissive Properties of Cyclometalated Iridium(III)-

Polypyridine Complexes in the Development of Luminescent

Biological Probes. Angew. Chem., Int. Ed. 2008, 47, 2213−2216.

(31) Chen, Y.; Qiao, L.; Ji, L.; Chao, H. Phosphorescent iridium(III)

complexes as multicolor probes for specific mitochondrial imaging and

tracking. Biomaterials 2014, 35, 2−13.

(32) Lo, K. K. W.; Zhang, K. Y. Iridium(III) complexes as therapeutic

and bioimaging reagents for cellular applications. RSC Adv. 2012, 2,

12069−12083.

(33) Liu, J.; Jin, C.; Yuan, B.; Liu, X.; Chen, Y.; Ji, L.; Chao, H.

Selectively lighting up two- photon photodynamic activity in

mitochondria with AIE-active iridium(III) complexes. Chem. Commun.

2017, 53, 2052−2055.

(34) Yu, M.; Zhao, Q.; Shi, L.; Li, F.; Zhou, Z.; Yang, H.; Yi, T.;

Huang, C. Cationic iridium(III) complexes for phosphorescence

staining in the cytoplasm of living cells. Chem. Commun. 2008, 2115−

2117.

(46) Lau, J. S.Y.; Lee, P. K.; Tsang, K. H. K.; Ng, C. H. C.; Lam, Y.

W.; Cheng, S. H.; Lo, K. K. W. Luminescent Cyclometalated

Iridium(III) Polypyridine Indole Complexes: Synthesis, Photophysics,

Electrochemistry, Protein-Binding Properties, Cytotoxicity, and

Cellular Uptake. Inorg. Chem. 2009, 48, 708−718.

(47) Lucas, S. J.; Lord, R. M.; Wilson, R. L.; Phillips, R. M.;

Sridharan, V.; McGowan, P. C. Synthesis of iridium and ruthenium

complexes with (N,N), (N,O) and (O,O) coordinating bidentate

ligands aspotential anti-cancer agents. Dalton Trans. 2012, 41, 13800.

(48) Liu, Z.; Habtemariam, A.; Pizarro, A. M.; Clarkson, G. J.; Sadler,

P. J. Organometallic Iridium(III) Cyclopentadienyl Anticancer

Complexes Containing C,N-Chelating Ligands. Organometallics

2011, 30, 4702−4710.

(49) Liu, Z.; Salassa, L.; Habtemariam, A.; Pizarro, A. M.; Clarkson,

G. J.; Sadler, P. J. Contrasting Reactivity and Cancer Cell Cytotoxicity

of Isoelectronic Organometallic Iridium(III) Complexes. Inorg. Chem.

2011, 50, 5777−5783.

́

(50) Millett, A. J.; Habtemariam, A.; Romero-Canelon, I.; Clarkson,

G. J.; Sadler, P. J. Contrasting Anticancer Activity of Half-Sandwich

Iridium(III) Complexes Bearing Functionally Diverse 2-Phenyl-

pyridine Ligands. Organometallics 2015, 34, 2683−2694.

(51) Ali Nazif, M.; Bangert, J. A.; Ott, I.; Gust, R.; Stoll, R.; Sheldrick,

W. S. Dinuclear Organoiridium(III) Mono- and Bis-intercalators with

Rigid Bridging Ligands: Synthesis, Cytotoxicity and DNA Binding. J.

Inorg. Biochem. 2009, 103, 1405−1414.

(52) Schafer, S.; Sheldrick, W. S. Coligand tuning of the DNA

̈

(35) Mukhopadhyay, S.; Gupta, R. K.; Paitandi, R. P.; Rana, N. K.;

Sharma, G.; Koch, B.; Rana, L. K.; Hundal, M. S.; Pandey, D. S.

Synthesis, Structure, DNA/Protein Binding, and Anticancer Activity of

Some Half-Sandwich Cyclometalated Rh(III) and Ir(III) Complexes.

Organometallics 2015, 34, 4491−4506.

binding properties of half-sandwich organometallic intercalators:

Influence of polypyridyl (pp) and monodentate ligands (L = Cl,

(NH₂)₂CS, (NMe₂)₂CS) on the intercalation of (g5-entamethylcyclo-

pentadienyl)-iridium(III)- dipyridoquinoxaline and dipyridophenazine

complexes. J. Organomet. Chem. 2007, 692, 1300−1309.

(53) Gupta, R. K.; Pandey, R.; Sharma, G.; Prasad, R.; Koch, B.;

Srikrishna, S.; Li, P. Z.; Xu, Q.; Pandey, D. S. DNA Binding and Anti-

Cancer Activity of Redox-Active Heteroleptic Piano-Stool Ru(II),

Rh(III), and Ir(III) Complexes Containing 4-(2 Methoxypyridyl)

phenyldipyrromethene. Inorg. Chem. 2013, 52, 3687−3698.

(54) Zhao, C.; Zhang, Y.; Wang, X.; Cao, J. Development of

BODIPY-based fluorescent DNA intercalating probes. J. Photochem.

Photobiol., A 2013, 264, 41−47.

(36) Wang, C.; Liu, J.; Tian, Z.; Tian, M.; Tian, L.; Zhao, W.; Liu, Z.

Half-sandwich iridium N-heterocyclic carbine anticancer complexes.

Dalton Trans. 2017, 46, 6870−6883.

(37) Tabrizi, L.; Chiniforoshan, H. New cyclometalated Ir(III)

complexes with NCN pincer and meso-phenylcyanamide BODIPY

ligands as efficient photodynamic therapy agents. RSC Adv. 2017, 7,

34160−34169.

(38) Loughrey, B. T.; Healy, P. C.; Parsons, P. G.; Williams, M. L.

Selective Cytotoxic Ru(II) Arene Cp* Complex Salts [R-

(55) Kamkaew, A.; Lim, S. H.; Lee, H. B.; Kiew, L. V.; Chung, L. Y.;

Burgess, K. BODIPY dyes in photodynamic therapy. Chem. Soc. Rev.

2013, 42, 77−88.

−

PhRuCp*]⁺X⁻for X = BF₄, PF₆, and BPh₄. Inorg. Chem. 2008,

47, 8589−8591.

N

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

(56) Gupta, G.; Das, A.; Park, K. C.; Tron, A.; Kim, H.; Mun, J.;

Mandal, N.; Chi, K. W.; Lee, C. Y. Self-Assembled Novel BODIPY-

Based Palladium Supramolecules and Their Cellular Localization.

Inorg. Chem. 2017, 56, 4615−4621.

(57) Paitandi, R. P.; Gupta, R. K.; Singh, R. S.; Sharma, G.; Koch, B.;

Pandey, D. S. Interaction of ferrocene appended Ru(II), Rh(III) and

Ir(III) dipyrrinato complexes with DNA/protein, molecular docking

and antitumor activity. Eur. J. Med. Chem. 2014, 84, 17−29.

(58) Gupta, R. K.; Sharma, G.; Pandey, R.; Kumar, A.; Koch, B.; Li, P.

Z.; Xu, Q.; Pandey, D. S. DNA/Protein Binding, Molecular Docking,

and in Vitro Anticancer Activity of Some Thioether-Dipyrrinato

Complexes. Inorg. Chem. 2013, 52, 13984−13996.

blebbing of biologically active organoselenium compound towards

human cervical cancer cell (HeLa): In vitro DNA/HSA binding,

cleavage and cell imaging studies. Eur. J. Med. Chem. 2015, 90, 876−

888.

(74) Keck, M. V.; Lippard, S. J. Unwinding of supercoiled DNA by

platinum-ethidium and related complexes. J. Am. Chem. Soc. 1992, 114,

3386−3390.

(75) Liu, Z. C.; Wang, B. D.; Yang, Z. Y.; Li, Y.; Qin, D. D.; Li, T. R.

Synthesis, crystal structure, DNA interaction and antioxidant activities

of two novel water-soluble Cu²⁺complexes derivated from 2-oxo-

quinoline-3-carbaldehyde Schiff-bases. Eur. J. Med. Chem. 2009, 44,

4477−4484.

(59) Srivastava, A.; Singh, R. M. Vilsmeier−Haack reagent:A facile

synthesis of 2-chloro3-formylquinolines from N-arylacetamides and

transformation into different functionalities. Indian J. Chem., Sect. B

2006, 37, 1868−1875.

(76) Paitandi, R. P.; Singh, R. S.; Mukhopadhyay, S.; Sharma, G.;

Koch, B.; Vishnoi, P.; Pandey, D. S. Synthesis, characterization, DNA

binding and cytotoxicity of fluoro-dipyrrin based arene ruthenium(II)

complexes. Inorg. Chim. Acta 2017, 454, 117−127.

(77) Senthil Raja, D.; Bhuvanesh, N. S. P.; Natarajan, K. Biological

evaluation of a novel water soluble sulphur bridged binuclear

copper(II) thiosemicarbazone complex. Eur. J. Med. Chem. 2011, 46,

4584−4594.

(78) Dang, C. V.; Ebert, R. F.; Bell, W. R. binding site between

gamma-subunit positions 311 and 336 by terbium fluorescence. J. Biol.

Chem. 1985, 260, 9713−9719.

(79) Ramachandran, E.; Thomas, S. P.; Poornima, P.; Kalaivani, P.;

Prabhakaran, R.; Padma, V. V.; Natarajan, K. Evaluation of DNA

binding, antioxidant and cytotoxic activity of mononuclear Co(III)

complexes of 2-oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde thi-

osemicarbazones. Eur. J. Med. Chem. 2012, 50, 405−415.

(80) Bhattacharyya, M.; Chaudhuri, U.; Poddar, R. K. Evidence for

cooperative binding of chlorpromazine with hemoglobin: Equilibrium

dialysis, fluorescence quenching and oxygen release study. Biochem.

Biophys. Res. Commun. 1990, 167, 1146−1153.

(60) Loudet, A.; Burgess, K. BODIPY Dyes and Their Derivatives:

Syntheses and Spectroscopic Properties. Chem. Rev. 2007, 107, 4891−

4932.

(61) Singh, R. S.; Gupta, R. K.; Paitandi, R. P.; Dubey, M.; Sharma,

G.; Koch, B.; Pandey, D. S. Morphological tuning via structural

modulations in AIE luminogens with the minimum number of possible

variables and their use in live cell imaging. Chem. Commun. 2015, 51,

9125−9128.

(62) Jacques, A.; Kirsch-De Mesmaeker, A.; Elias, B. Selective DNA

Purine Base Photooxidation by Bis-terdentate Iridium(III) Polypyridyl

and Cyclometalated Complexes. Inorg. Chem. 2014, 53, 1507−1512.

(63) Nakagawa, A.; Hisamatsu, Y.; Moromizato, S.; Kohno, M.; Aoki,

S. Selective DNA Purine Base Photo-oxidation by Bis-terdentate

Iridium(III) Polypyridyl and Cyclometalated Complexes. Inorg. Chem.

2014, 53, 409−422.

(64) Hanson, K.; Tamayo, A.; Diev, V. V.; Whited, M. T.; Djurovich,

P. I.; Thompson, M. E. Efficient Dipyrrin-Centered Phosphorescence

at Room Temperature from Bis-Cyclometalated Iridium(III) Dipyrri-

nato Complexes. Inorg. Chem. 2010, 49, 6077−6084.

(81) Wang, C. X.; Yan, F. F.; Zhang, Y. X.; Ye, L. Spectroscopic

investigation of the interaction between rifabutin and bovine serum

albumin. J. Photochem. Photobiol., A 2007, 192, 23−28.

(65) Mukhopadhyay, S.; Singh, R. S.; Biswas, A.; Maiti, B.; Pandey,

D. S. Molecular and Nanoaggregation in Cyclometalated Iridium(III)

Complexes through Structural Modification. Eur. J. Inorg. Chem. 2016,

2016, 4199−4206.

(66) Madhu, S.; Kumar, S.; Chatterjee, T.; Ravikanth, M. Synthesis,

X-ray structure, spectral and electrochemical properties of a b-meso

covalently linked BODIPY−Ru(II) dipyrrin complex. New J. Chem.

2014, 38, 5551−5558.

(67) Rachford, A. A.; Ziessel, R.; Bura, T.; Retailleau, P.; Castellano,

F. N. Boron Dipyrromethene (Bodipy) Phosphorescence Revealed in

[Ir(ppy)₂(bpy-C≡C-Bodipy)]⁺. Inorg. Chem. 2010, 49, 3730−3736.

(68) Wang, T.; Hou, Y.; Chen, Y.; Li, K.; Cheng, X.; Zhou, Q.; Wang,

X. Two novel BODIPY−Ru(II) arene dyads enabling effective photo-

inactivation against cancer cells Dalton. Trans. 2015, 44, 12726−

12734.

(82) Raja, D. S.; Bhuvanesh, N. S. P.; Natarajan, K. A novel water

soluble ligand bridged cobalt(II) coordination polymer of 2-oxo-1,2-

dihydroquinoline-3-carbaldehyde (isonicotinic) hydrazone: evaluation

of the DNA binding, protein interaction, radical scavenging and

anticancer activity. Dalton Trans. 2012, 41, 4365−4375.

(83) Miller, J. N. Recent advances in molecular luminescence

analysis. Proc. Anal. Div. Chem. Soc. 1979, 16, 203−208.

(84) Burstein, E. A.; Vedenkina, N. S.; Ivkova, M. N. Fluorescence

and the location of tryptophan residues in protein molecules.

Photochem. Photobiol. 1973, 18, 263−279.

(85) Bernhardt, P. V.; Sharpe, P. C.; Islam, M.; Lovejoy, D. B.;

Kalinowski, D. S.; Richardson, D. R. Iron Chelators of the

Dipyridylketone Thiosemicarbazone Class: Precomplexation and

Transmetalation Effects on Anticancer Activity. J. Med. Chem. 2009,

52, 407−415.

(69) Ganeshpandian, M.; Loganathan, R.; Suresh, E.; Riyasdeen, A.;

Akbarsha, M. A.; Palaniandavar, M. New ruthenium(II) arene

complexes of anthracenyl-appended diazacycloalkanes: effect of ligand

intercalation and hydrophobicity on DNA and protein binding and

cleavage and cytotoxicity. Dalton Trans. 2014, 43, 1203−1219.

(70) Alagesan, M.; Sathyadevi, P.; Krishnamoorthy, P.; Bhuvanesh,

N. S. P.; Dharmaraj, N. DMSO containing ruthenium(II) hydrazone

complexes: in vitro evaluation of biomolecular interaction and

anticancer activity. Dalton Trans. 2014, 43, 15829−15840.

(71) Kilpin, K. J.; Clavel, C. M.; Edafe, F.; Dyson, P. J.

Naphthalimide-Tagged Ruthenium−Arene Anticancer Complexes:

Combining Coordination with Intercalation. Organometallics 2012,

31, 7031−7039.

(72) Hu, K.; Li, F.; Zhang, Z.; Liang, F. Synthesis of two potential

anticancer copper(II) complex drugs: their crystal structure, human

serum albumin/DNA binding and anticancer mechanism. New J.

Chem. 2017, 41, 2062−2072.

(73) Rizvi, M. A.; Zaki, M.; Afzal, M.; Mane, M.; Kumar, M.; Shah, B.

A.; Srivastav, S.; Srikrishna, S.; Peerzada, G. M.; Tabassum, S. Nuclear

(86) Tong, J. Q.; Tian, F. F.; Li, Q.; Li, L. L.; Xiang, C.; Liu, Y.; Dai,

J.; Jiang, F. L. Probing the adverse temperature dependence in the

static fluorescence quenching of BSA induced by a novel anticancer

hydrazon. Photochem. Photobiol. Sci. 2012, 11, 1868−1879.

(87) Holm, A. I. S.; Nielsen, L. M.; Hoffmann, S. V.; Nielsen, S. B.

Vacuum-ultraviolet circular dichroism spectroscopy of DNA: A

valuable tool to elucidate topology and electronic coupling in DNA.

Phys. Chem. Chem. Phys. 2010, 12, 9581−9596.

(88) Chang, Y. M.; Chen, C. K. M.; Hou, M. H. Conformational

changes in DNA upon ligand binding monitored by circular dichroism.

Int. J. Mol. Sci. 2012, 13, 3394−3413.

(89) Cutts, S. M.; Masta, A.; Panousis, C.; Parsons, P. G.; Sturm, R.

A.; Phillips, D. R. A Gel Mobility Shift Assay for Probing the Effect of

Drug−DNA Adducts on DNA-Binding Proteins. Drug-DNA Interact,

Protocols 1997, 90, 95−106.

(90) Suh, D.; Chaires, J. B. Criteria for the mode of binding of DNA

binding agents. Bioorg. Med. Chem. 1995, 3, 723−728.

(91) Rajendiran, V.; Murali, M.; Suresh, E.; Sinha, S.; Somasundaram,

K.; Palaniandavar, M. Mixed ligand ruthenium(II) complexes of

O

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

bis(pyrid-2-yl)-/bis(benzimidazol- 2-yl)-dithioether and diimines:

Study of non-covalent DNA binding and cytotoxicity. Dalton Trans.

2008, 148−163.

(106) Lee, C. T.; Yang, W. T.; Parr, R. G. Development of the Colle-

Salvetti correlation-energy formula into a functional of the electron

density. Phys. Rev. B: Condens. Matter Mater. Phys. 1988, 37, 785−789.

(107) Berridge, M. V.; Herst, P. M.; Tan, A. S. Tetrazolium dyes as

tools in cell biology: new insights into their cellular reduction.

Biotechnol. Annu. Rev. 2005, 11, 127−152.

(92) Kelly, J. M.; Tossi, A. B.; McConnell, D. J.; OhUigin, O. A study

of the interactions of some polypyridylruthenium (II) complexes with

DNA using fluorescence spectroscopy, topoisomerisation and thermal

denaturation. Nucleic Acids Res. 1985, 13, 6017−6034.

(108) Mukhopadhyay, S.; Singh, R. S.; Paitandi, R. P.; Sharma, G.;

Koch, B.; Pandey, D. S. Influence of Substituents on DNA/ Protein

Binding and Anticancer Activity of Cyclometalated Ir(III) Complexes.

Dalton Trans. 2017, 46, 8572−8585.

́

(93) Inclan, M.; Albelda, M. T.; Frías, J. C.; Blasco, S.; Verdejo, B.;

́

Serena, C.; Salat-Canela, C.; Díaz, M. L.; Garcıa-Espana, A.; Garcıa-

̃

Espana, E. Modulation of DNA Binding by Reversible Metal-

̃

(109) Bezabeh, T.; Mowat, M. R. A.; Jarolim, L.; Greenberg, A. H.;

Smith, I. C. P. Detection of drug-induced apoptosis and necrosis

Controlled Molecular Reorganizations of Scorpiand-like Ligands. J.

Am. Chem. Soc. 2012, 134, 9644−9656.

1

inhuman cervical carcinoma cells using H NMR spectroscopy. Cell

(94) Martins, S.; Sarmento, B.; Ferreira, D. C.; Souto, E. B. Lipid-

based Colloidal Carriers for Peptide and Protein Delivery-liposomes

Versus Lipid Nanoparticles. Int. J. Nanomed. 2007, 2, 595−607.

(95) Oldfield, S. P.; Hall, M. D.; Platts, J. A. Calculation of

Lipophilicity of a Large, Diverse Dataset of Anticancer Platinum

Complexes and the Relation to Cellular Uptake. J. Med. Chem. 2007,

50, 5227−5237.

(96) Vock, C. A.; Renfrew, A. K.; Scopelliti, R.; Juillerat-Jeanneret, L.;

Dyson, P. J. Influence of the Diketonato Ligand on the Cytotoxicities

of [Ru(η⁶-p-cymene)(R₂acac)(PTA)]⁺Complexes (PTA = 1,3,5-

triaza-7-phosphaadamantane). Eur. J. Inorg. Chem. 2008, 2008, 1661−

1671.

Death Differ. 2001, 8, 219−224.

(110) Perrin, D. D.; Armango, W. L. F.; Perrin, D. R. Puriﬁcation of

laboratory Chemicals; Pergamon: Oxford, U.K., 1986.

(111) Sheldrick, G. M. SHELXL-97, Program for X-ray Crystal

Structure Reﬁnement; Gottingen University: Gottingen, Germany, 1997.

(112) Sheldrick, G. M.; SHELXS-97, Program for X-ray Crystal

Structure Solution; Gottingen University: Gottingen, Germany, 1997.

(113) Spek, A. L. PLATON, A Multipurpose Crystallographic Tools;

Utrecht University: Utrecht, The Netherlands, 2000.

(114) Spek, A. L. Acta Crystallogr., Sect. A 1990, 46, C31.

(97) Mustard, D.; Ritchie, D. W. Docking essential dynamics

eigenstructures. Proteins: Struct., Funct., Genet. 2005, 60, 269−274.

(98) Husain, M. A.; Sarwar, T.; Rehman, S. U.; Ishqi, H. M.; Tabish,

M. Ibuprofen causes photocleavage through ROS generation and

intercalates with DNA: a combined biophysical and molecular docking

approach. Phys. Chem. Chem. Phys. 2015, 17, 13837−13850.

(99) Tabassum, S.; Zaki, M.; Afzal, M.; Arjmand, F. New Modulated

Design and Synthesis of Quercetin-Cu(II)/Zn(II)-Sn₂(IV) Scaffold as

Anticancer Agents: In vitro DNA Binding Profile, DNA Cleavage

Pathway and Topo-I Activity. Dalton Trans. 2013, 42, 10029−10041.

(100) Filosa, R.; Peduto, A.; Micco, S. D.; Caprariis, P. D.; Festa, M.;

Petrella, A.; Capranico, G.; Bifulco, G. Molecular Modelling Studies,

Synthesis and Biological Activity of a Series of Novel Bisnaphthali-

mides and their Development as New DNA Topoisomerase II

Inhibitors. Bioorg. Med. Chem. 2009, 17, 13−24.

(101) Tabassum, S.; Al-Asbahy, W. M.; Afzal, M.; Arjmand, F.; Hasan

Khan, R. Interaction and Photo-induced Cleavage Studies of a Copper

Based Chemotherapeutic Drug with Human Serum Albumin:

Spectroscopic and Molecular Docking Study. Mol. BioSyst. 2012, 8,

2424−2433.

(102) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;

Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci,

B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H.

P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.;

Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima,

T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.;

Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin,

K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.;

Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega,

N.; Millam, N. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.;

Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.;

Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.;

Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.;

̈

Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.;

Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09,

revision A.1; Gaussian, Inc.: Wallingford, CT, 2009.

(103) Krishnan, R.; Binkley, J. S.; Seeger, R.; Pople, J. A. Self-

consistent molecular orbital methods. XX. A basis set for correlated

wave functions. J. Chem. Phys. 1980, 72, 650.

(104) Wadt, W. R.; Hay, P. Ab initio effective core potentials for

molecular calculations. Potentials for main group elements Na to Bi. J.

Chem. Phys. 1985, 82, 284.

(105) Becke, A. D. Density-functional thermochemistry. III. The role

of exact exchange. J. Chem. Phys. 1993, 98, 5648.

P

DOI: 10.1021/acs.inorgchem.7b01693

Inorg. Chem. XXXX, XXX, XXX−XXX

Article Doi

Anticancer Activity of Iridium(III) Complexes Based on a Pyrazole-Appended Quinoline-Based BODIPY

DOI: 10.1021/acs.inorgchem.7b01693

Source and publish data:

Authors:

Article abstract of DOI:10.1021/acs.inorgchem.7b01693

Full text of DOI:10.1021/acs.inorgchem.7b01693

Products guided by the article

R&D Labs maybe for 73568-29-3

Relevant to this article

Hot Product