NLO active CuII/RuII and CdII/RuII coordination-organometallic complexes: synthesis, structural characterization and photoluminescence properties

Article abstract of DOI:10.1080/00958972.2016.1229475

Cu^II/Ru^II and Cd^II/Ru^II hybrid complexes [Cu(L_1–3)(NC₅H₄C≡CRu(dppe)₂Cl)] (1a-3a) and [Cd(L_1-3)(NC₅H₄C≡CRu(dppe)₂Cl)] (1b–3b

Full text of DOI:10.1080/00958972.2016.1229475

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
NLO active CuII/RuII and CdII/RuII coordination-
organometallic complexes: synthesis, structural
characterization and photoluminescence
properties
B. G. Bharate & S. S. Chavan
To cite this article: B. G. Bharate & S. S. Chavan (2016): NLO active CuII/RuII and CdII/
RuII coordination-organometallic complexes: synthesis, structural characterization
and photoluminescence properties, Journal of Coordination Chemistry, DOI:
10.1080/00958972.2016.1229475
To link to this article: http://dx.doi.org/10.1080/00958972.2016.1229475
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Date: 16 September 2016, At: 09:35

Journal of Coordination Chemistry, 2016
http://dx.doi.org/10.1080/00958972.2016.1229475
NLO active CuII/RuII and CdII/RuII coordination-organometallic
complexes: synthesis, structural characterization and
photoluminescence properties
B. G. Bharatea,b and S. S. Chavana
adepartment of Chemistry, shivaji university, Kolhapur, india; bdepartment of applied Chemistry, defence institute
of advanced technology (du), Pune, india
ABSTRACT
ARTICLE HISTORY
received 5 april 2016
accepted 19 July 2016
CuII/RuII and CdII/RuII hybrid complexes [Cu(L1–3)(NC5H4C≡CRu(dppe)2Cl)]
(1a-3a) and [Cd(L1-3)(NC5H4C≡CRu(dppe)2Cl)] (1b–3b) have been prepared
by reaction of trans-[RuCl(dppe)2(C≡C-py-3)] (1) with copper or cadmium
acetate in the presence of Schiff base ligands LH1–3 (where LH = 2-(pyrrole-
2-yl-methylidine)aminophenol (LH1), 5-bromo-2-(pyrrole-2-yl-methylidine)
aminophenol (LH2) and 5-nitro-2-(pyrrole-2-yl-methylidine)aminophenol
(LH3)). The hybrid materials were characterized on the basis of elemental
KEYWORDS
schiff base; hybrid
complexes; fluorescence;
nonlinear optics
analyses, TEM, IR, UV–visible, H NMR, and 31P NMR spectral studies. TEM
1
overview observations revealed well-dispersed spherical nanoparticles of
~60 nm are formed. Quasireversible redox behavior is observed for CuII/RuII
complexes corresponding to CuI/CuII and RuII/RuIII couples. All the complexes
exhibit blue-green emission as a result of fluorescence from the intraligand
(π → π*) emission excited state with good quantum yield. The second-order
nonlinear optical (NLO) properties of CuII/RuII and CdII/RuII complexes have
been investigated by the Kurtz-powder method. The second harmonic
generation efficiency of these complexes show that these complexes are
NLO active and display good second-order nonlinear optical activity.
CONTACT B. G. Bharate
bgbharate@rediffmail.com
supplemental data for this article can be accessed at http://dx.doi.org/10.1080/00958972.2016.1229475.
© 2016 informa uK limited, trading as taylor & francis Group

2
B. G. BHARATE ANd S. S. CHAVAN
1. Introduction
There has been interest in the development of better NLO materials due to their potential applications in
optical devices such as optical signal processing, switching, frequency generation, optical data storage,
optical communication, and image processing [1–4]. The most widely used NLO materials are inorganic
crystals such as LiB3O5, BaB2O4, and KH2PO4. Organic NLO crystals have superior properties to inorganic
ones, such as higher susceptibility faster response and the capability of designing components on the
molecular level. Effort has been devoted to the metal organic coordination complexes as NLO materi-
als due to high NLO coefficient, stable physicochemical properties, and better mechanical intension,
combining the useful attributes of both organic and inorganic components. The advantage of metal
organic coordination complexes are wide variety of central metals varying in size, nature, oxidation
states, as well as ligands with different nature and size, facilitating the development of relationships
between molecular structures and NLO properties. The most challenging goal to the chemist is to
develop new π-conjugated materials with new branches and core to investigate their physical and
chemical properties as well as their structure property relationships [5–11].
Metal organic coordination complexes have been growing at a phenomenal rate because of their
unique structural, electronic, and functional properties. We are interested in organic and inorganic
components of Ru-based hybrid systems to construct structurally organized molecular materials. As
continuation of our research we report herein synthesis, characterization, photoluminescence, and
nonlinear optical properties of MII/RuII (M=Cu, Cd) Schiff base complexes by reaction of trans-[RuCl(dp-
pe)2(C≡C-py-3)] (1) with copper or cadmium acetate in the presence of Schiff base ligands LH1–3 (where

JOURNAL Of COORdINATION CHEMISTRy
3
L = 2-(pyrrole-2-yl-methylidine)aminophenol (LH1), 5-bromo-2-(pyrrole-2-yl-methylidine)amino phenol
(LH2) and 5-nitro-2-(pyrrole-2-yl-methylidine)aminophenol (LH3)).
All complexes were characterized by TEM, elemental analyses, IR, UV–visible, 1H NMR, and 31P NMR
spectral studies. The photoluminescence, electrochemical behavior, and SHG efficiencies of the com-
plexes have been studied.
2. Experimental
2.1. Materials and general methods
All the chemicals used were of analytical grade. Solvents for synthesis were distilled over appropriate dry-
ing agents. trans-[RuCl(dppe)2(C≡C-py-3)] (1) was prepared by our previously reported procedure with
high yield and purity. Copper acetate, cadmium acetate, and 2-aminophenol were from Spectrochem
and 3-ethynylpyridine, NaPf6, RuCl3·xH2O, PdCl2(PPh3)2, and nBu4NPf6 were obtained from Aldrich and
used as received.
Elemental analyses were performed on a Thermo finnigan fLASH EA-112 CHNS analyzer. Electronic
spectra were recorded on a Cyber-Lab UV-100 Superspec spectrophotometer. Infrared spectra were
recorded on a Perkin Elmer fT-IR spectrometer as KBr pellets from 4000–400 cm−1. 1H NMR spectra of
the samples were measured on a Varian Mercury-300 MHz instrument usingTMS as an internal standard.
31P NMR spectra were recorded using a Varian Mercury-300 fT NMR spectrometer. ESI mass spectra of
all the complexes were recorded using a Bruker Apex3. Thermal analyses of the complexes were car-
ried out on a Perkin Elmer thermal analyzer in nitrogen at a heating rate of 10 °C/min. Luminescence
properties were determined using a JASCO f.P.750 fluorescence spectrophotometer equipped with
a quartz cuvette of 1 cm3 path length at room temperature. Cyclic voltammetry measurements were
performed with a CH-400A Electrochemical Analyzer. A standard three electrode system consisting
of Pt disk working electrode, Pt wire counter electrode, and Ag/AgCl reference electrode containing
aqueous 3 M KCl were used.
2.2. Synthesis of LH1–3
2.2.1. Synthesis of 2-(pyrrole-2-yl-methylidine)aminophenol (LH1)
A solution of pyrrole-2-carboxyaldehyde (0.35 g, 3.68 mmol) in 15 mL methanol was added dropwise
to a dissolved solution of 2-amino phenol (0.40 g, 3.68 mmol) in methanol (10 mL) with constant stir-
ring at room temperature and the resulting mixture was refluxed at 70 °C until completion of reaction
(reaction monitored byTLC). The resultant dark brown product was purified by column chromatography.
The solvent was removed under vacuum by a rotary evaporator to receive dark brown product. yield:
(0.51 g, 75%); IR (KBr) (cm−1): 3145, υ(N–H); 1618, υ(HC=N); 1283, υ(C–O); 1H NMR (CdCl3) (300 MHz): δ
11.74 (bs, –OH), 8.72 (s, HC=N), 6.74–7.27 (m, Ar–H); MS: 186 (M+).
2.2.2. Synthesis of 5-bromo-2-(pyrrol-2-yl-methylidine)aminophenol (LH2)
LH2 was prepared similar to the procedure performed in the preparation of LH1 except that 2-amino-phe-
nol was replaced by 2-amino-5-bromo phenol (0.69 g, 3.68 mmol). yield: (0.69 g, 70%); IR (KBr) (cm−1):
3139, υ(N–H); 1620, υ(HC=N); 1279, υ(C–O); 1H NMR (CdCl3) (300 MHz): δ 11.76 (bs, –OH), 8.74 (s, HC=N),
6.68–7.29 (m, Ar–H); MS: 265 (M+).
2.2.3. Synthesis of 5-nitro-2-(pyrrol-2-yl-methylidine)aminophenol (LH3)
LH3 was prepared similar to the procedure performed in the preparation of LH1 except that 2-amino
phenol is replaced by 2-amino-5-nitrophenol (0.57 g, 3.68 mmol). yield: (0.58 g, 68%); IR (KBr) (cm−1):
3135, υ(N–H); 1625, υ(HC=N); 1281, υ(C–O); 1H NMR (CdCl3) (300 MHz): δ 11.72 (bs, –OH), 8.75 (s, HC=N),
6.71–7.31 (m, Ar–H); MS: 231(M+).

4
B. G. BHARATE ANd S. S. CHAVAN
2.3. Synthesis of CuII/RuII hybrid complexes (1a-3a)
2.3.1. Synthesis of [Cu(L1)NC5H4C≡CRu(dppe)2Cl] (1a)
To a solution of trans-[RuCl(dppe)2(C≡C-py-3)] (1) (0.200 g, 0.193 mmol) in CH2Cl2 was added a solution
of Cu(CH3COO)2·H2O (0.038 g, 0.193 mmol) and LH1 (0.036 g, 0.193 mmol) in MeOH dropwise with con-
stant stirring. The reaction mixture was then refluxed for 6 h and the resulting solution was evaporated
to small volume under vacuum. The dark yellow complex was collected by filtration, washed with
ethanol, and dried in vacuo. yield: (0.192 g, 72%); Elemental analyses (C, H, and N, wt %) Anal. Calcd for
C70H60N3RuP4OClCu: C, 65.52; H, 4.71; N, 3.27. found: C, 65.38; H, 4.67; N, 3.41. IR (KBr) (cm−1): 2051 υ(C≡C);
1590, υ(HC=N); 1261, υ(C–O); 1476, 1432, 1167, 695, υ(dppe); 491 υ(M-N); UV–Vis (dMf) λmax (nm) (ε × 103,
M−1 cm−1): 241 (24), 283 (13), 381(6); 514 (1.2); 1H NMR (dmso-d6) (300 MHz): δ 8.95 (s, HC=N), 8.13 (s,
1H, Py-HoN,oC≡C), 8.04 (d, 1H, Py-HoN,pC≡C), 6.56–7.19 (m, 49 H, phenyl), 2.65 (s, 8H, PCH2CH2P); 31P NMR: δ
46.62. ESI MS: 1306 ([Cu(L1)NC5H4C≡CRu(dppe)2Cl + Na]+, 13); 1105 ([CuNC5H4C≡CRu(dppe)2Cl)]+, 28);
1041 ([NC5H4C≡CRu(dppe)2Cl)]+, 100); 898 ([Ru(dppe)2-]+12).
2.3.2. Synthesis of [Cu(L2)NC5H4C≡CRu(dppe)2Cl] (2a)
Complex 2a was prepared similar to the procedure performed in the preparation of 1a except that
LH1 was replaced by LH2 (0.051 g, 0.193 mmol). yield (0.192 g, 78%); Elemental analyses (C, H and N,
wt %) Anal. Calcd for C70H59N3RuP4OCuClBr; C, 61.72; H, 4.37; N, 3.08. found: C, 61.39; H, 4.21; N, 3.17.
IR (KBr) (cm1): 2058 υ(C≡C); 1591 υ(HC=N); 1264, υ(C–O); 1470, 1431, 1165, 691 (dppe); 509 υ(M–N);
1
UV–Vis (dMf) λmax (nm) (ε × 103, M−1 cm−1): 242 (19), 282(11), 382 (7); 517 (0.9); H NMR (dmso-d6)
(300 MHz), δ 9.13 (s, HC=N), 8.15 (s, 1H, Py-HoN,oC≡C), 8.01 (d,1H, Py-HoN,pC≡C), 6.75–7.84 (m,48 H, phenyl),
2.63 (s, 8H, PCH2CH2P); 31P NMR: δ 46.53. ESI MS: 1385 ([Cu(L2)NC5H4C≡CRu(dppe)2Cl + Na]+, 17); 1105
([CuNC5H4C≡CRu(dppe)2Cl)]+, 23); 1041 ([NC5H4C≡CRu(dppe)2Cl]+, 100); 898 ([Ru(dppe)2]+07).
2.3.3. Synthesis of [Cu(L3)NC5H4C≡CRu(dppe)2Cl] (3a)
Complex 3a was prepared similar to the procedure performed in the preparation of 1a except that
LH1 was replaced by LH3 (0.044 g, 0.193 mmol). yield: (0.186 g, 69%); Elemental analyses (C, H, and N,
wt %) Anal. Calcd for C70H59N4RuP4O3CuCl: C, 63.30; H, 4.48; N, 4.22. found: C, 62.89; H, 4.39; N, 4.36.
IR (KBr) (cm-1): 2047 υ(C≡C); 1598, υ(HC=N); 1268, υ(C–O); 1485, 1432, 1174, 695, υ(dppe); 482 υ(M-
N); UV–Vis (dMf) λmax (nm) (ε × 103, M−1 cm−1): 249 (24); 281(13), 392 (8); 519 (1.2); 1H NMR (dmso-d6)
(300 MHz), δ 9.15 (s, HC=N), 8.04 (s, 1H, Py-HoN,oC≡C), 8.01 (d, 1H, Py-HoN,pC≡C), 6.52–7.69 (m, 48 H, phenyl),
2.71 (s, 8H, PCH2CH2P); 31P NMR: δ 46.87. ESI MS: 1351 ([Cu(L3)NC5H4C≡CRu(dppe)2Cl + Na]+,22); 1105
([CuNC5H4C≡CRu(dppe)2Cl)]+, 29); 1041 ([CuNC5H4C≡CRu(dppe)2Cl)]+, 100); 898 ([Ru(dppe)2]+ 11).
2.4. Synthesis of CdII/RuII hybrid complexes (1b-3b)
2.4.1. Synthesis of [Cd(L1)NC5H4C≡CRu(dppe)2Cl] (1b)
To a solution of trans-[RuCl(dppe)2(C≡C-py-3)] (1) (0.200 g, 0.193 mmol) in CH2Cl2 was added a solution
of Cd(CH3COO)2·2H2O (0.051 g, 0.193 mmol) and LH1 (0.036 g, 0.193 mmol) in MeOH dropwise with
constant stirring. The reaction mixture was then refluxed for 6 h and the resulting solution then evap-
orated to small volume under vacuum. The pale yellow complex was collected by filtration, washed
with ethanol, and dried in vacuo. yield (0.184 g, 71%). Elemental analyses (C, H, and N, wt %) Anal. Calcd
for C70H60N3RuP4OCdCl: C, 63.12; H, 4.54; N, 3.15. found: C, 62.85; H, 4.21; N, 3.21. IR (KBr) (cm−1): 2053
υ(C≡C); 1588, υ(HC=N); 1267, υ(C–O); 1481, 1435, 1095, 693, υ (dppe); 512 υ(M–N); UV–Vis (dMf) λmax
(nm) (ε × 103, M−1 cm−1): 246 (26); 278 (12); 379 (8); 1H NMR (dmso-d6) (300 MHz): δ 9.01 (s, HC=N), 8.15
(s, 1H, Py-HoN,oC≡C), 8.01 (d, 1H, Py-HoN,pC≡C), 6.59–7.25 (m, 49 H, phenyl), 2.69 (s, 8H, PCH2CH2P); 31P NMR:
δ 46.74. ESI MS: 1355 ([Cd(L1)NC5H4C≡CRu(dppe)2Cl + Na]+, 18); 1153 ([CuNC5H4C≡CRu(dppe)2Cl)]+, 18);
1041 ([CuNC5H4C≡CRu(dppe)2Cl)]+, 100); 898 ([Ru(dppe)2]+15).

JOURNAL Of COORdINATION CHEMISTRy
5
2.4.2. Synthesis of [Cd(L2)NC5H4C≡CRu(dppe)2Cl] (2b)
Complex 2b was prepared similar to the procedure performed in the preparation of 1b except that
LH1 was replaced by LH2 (0.0512 g, 0.193 mmol). yield: (0.202 g, 74%); Elemental analyses (C, H and
N, wt %) Anal. Calcd for C70H59N3RuP4OCdClBr: C, 59.59; H, 4.21; N, 2.98. found: C, 59.12; H, 4.01;
N, 3.13. IR (KBr) (cm−1): 2051 υ(C≡C); 1601, υ(HC=N); 1262, υ(C–O); 1482, 1434, 1159, 691, υ(dppe);
487, υ(M-N); UV–Vis (dMf) λmax (nm)(ε × 103, M−1 cm−1): 249 (27); 279 (13); 378 (9); 1H NMR (dmso-d6)
(300 MHz), δ 9.12 (s, HC=N), 8.12 (s, 1H, Py-HoN,oC≡C), 8.04 (d,1H, Py-HoN,pC≡C), 6.93–7.42 (m,48 H, phenyl),
2.69 (s, 8H, PCH2CH2P); 31P NMR: δ 46.58. ESI MS: 1434 ([Cd(L2)NC5H4C≡CRu(dppe)2Cl + Na]+, 10), 1149
([CdNC5H4C≡CRu(dppe)2Cl)]+, 14) 1041([NC5H4C≡CRu(dppe)2Cl]+, 100), 957 ([Ru(dppe)2]ClNa.]+ 21).
2.4.3. Synthesis of [Cd(L3)NC5H4C≡CRu(dppe)2Cl] (3b)
Complex 3b was prepared similar to the procedure performed in the preparation of 1b except that
LH1 was replaced by LH3 (0.0446 g, 0.193 mmol). yield: (0.190 g, 76%); Elemental analyses (C, H, and N,
wt %) Anal. Calcd for C70H59N4RuP4O3CdCl: C, 61.05; H, 4.32; N, 4.07. found: C, 60.87; H, 4.02; N, 4.28.
IR (KBr) (cm−1): 2054 υ(C≡C); 1605, υ(HC=N); 1261, υ(C–O); 1478, 1439, 1166, 693, υ(dppe); 495 υ(M-N);
1
UV–Vis (dMf) λmax (nm)(ε × 103, M−1 cm−1): 252 (28); 280 (14); 381 (7); H NMR (dmso-d6) (300 MHz),
δ 9.06 (s, HC=N), 8.04 (s, 1H, Py-HoN,oC≡C), 8.01 (d, 1H, Py-HoN,pC≡C), 6.57–7.62 (m, 48 H, phenyl), 2.68
(s, 8H, PCH2CH2P); 31P NMR: δ 46.82. ESI MS: 1400 ([Cd(L3)NC5H4C≡CRu(dppe)2Cl + Na]+, 29); 1153
([CdNC5H4C≡CRu(dppe)2Cl)]+, 31) 1041 ([CuNC5H4C≡CRu(dppe)2Cl)]+, 100), 898 ([Ru(dppe)2]+ 12).
3. Results and discussion
3.1. Synthesis and characterization
The reaction of equimolar quantities of trans-[RuCl(dppe)2(C≡C-py-3)] (1) with CuII or CdII acetate
in the presence of Schiff base ligands LH1–3 in CH2Cl2/MeOH afforded bimetallic complexes [Cu(L1-3
)
(NC5H4C≡CRu(dppe)2Cl)] (1a-3a) and [Cd(L1–3)(NC5H4C≡CRu(dppe)2Cl)] (1b-3b) (where L=2-(pyrrole-
2-yl-methylidine)aminophenol-H (L1), 5-bromo-2-(pyrrole-2-yl-methylidine)aminophenol-H (L2) and
5-nitro-2-(pyrrole-2-yl-methylidine)aminophenol-H (L3)]. CuII is one of the most labile metal centers
even though it forms air stable, moisture insensitive complexes due to π-acceptor ability of ligands.
These complexes are partially soluble in chloroform, dichloromethane, methanol, etc., but show max-
imum solubility in dMf and dMSO. All the complexes were characterized by elemental analyses, IR,
UV–Visible, 1H NMR, and 31P NMR spectral studies. The results of elemental analyses confirm the com-
positions of the complexes.
To study the bonding of LH1–3 and organometallic moiety 1 to CuII or CdII, IR spectra of LH1–3 and 1 are
compared with the spectra of their corresponding binuclear complexes. The IR spectrum of 1 shows
the band at 2074 cm−1 corresponding to C≡C bonds of pyridyl acetylide ligand; upon coordination
this band shifted to lower frequency at ca. 2047–2058 cm−1 for 1a-3a and 2051–2054 cm−1 for 1b-3b
[12]. The band at 1618–1625 cm−1 in spectra of uncomplexed LH1–3 is due to υ(HC=N), shifted to lower
frequency at 1590–1598 cm−1 in 1a-3a and 1588–1605 cm−1 in 1b-3b, indicating involvement of imine
(HC=N) nitrogen in coordination with the metal ion [13]. A new band at ca. 482–512 cm−1 is observed
in all complexes which is not present in either LH1–3 nor in 1, which is assigned to υ(M–N) stretch. The
involvement of deprotonated phenolic moiety in all heterobimetallic complexes is confirmed by shift of
the stretching band at 1279–1283 cm−1 in LH1–3 to lower frequency by 10–20 cm−1. The shift of υ(C–O) at
1283 cm−1 to lower frequency suggests weakening of υ(C–O) and formation of strong M–O bonds [14].
The N-H stretching frequency of LH1–3 at 3135–2900 cm−1 disappeared in all heterometallic complexes,
indicating participation of deprotonated N-H [15]. The spectra of all complexes also exhibit bands for
dppe ligand at 1483, 1435, 1168, and 693 cm−1 [16].
Electronic absorption spectra of 1a-3a and 1b-3b were measured in dMf solution at room tem-
perature. The spectra show intense bands at ca. 241–249 and 278–283 nm for 1a-3a and 249–252 and
278–281 nm for 1b-3b assigned to π → π* and n → π* transitions of the coordinated ligands. In addition

6
B. G. BHARATE ANd S. S. CHAVAN
Figure 1. Proposed molecular structure of the complexes.
to the high energy band, low energy absorptions at ca. 381–392 nm in 1a-3a and 378–382 nm in 1b-
3b are likely assigned as a mixture of intraligand (π → π*) transition with metal-ligand charge transfer
(MLCT) transitions, similar to their precursor complexes [17]. The slight bathochromic shift in these
complexes relative to 1 indicates coordination of the pyridyl group to CuII or CdII. A very weak absorption
at 519 nm for 1a-3a which is absent in 1b-3b is assigned for d-d transition of four-coordinate square
planer geometry around CuII [18].
1H NMR spectra of 1a-3a and 1b-3b recorded in dmso-d6 are given in the Experimental section. The
1H NMR spectroscopic data of 1a-3a and 1b-3b are consistent with their formulation as heterometallic
ruthenium acetylide complexes. A comparison of the chemical shifts of 1 with 1a-3a and 1b-3b shows
that some of the resonances are shifted on complexation in each case. The 1H NMR spectra of LH1–3 shows
a singlet at δ 8.72–8.75 ppm for imine proton. This imine proton signal is easily identified as a singlet at δ
8.79–9.15 ppm for 1a-3a and 9.01–9.12 ppm for 1b-3b. downfield shift of imine proton signal of complex
as compared to LH1–3 is attributed to deshielding arising from coordination of imine nitrogen [19, 20]. The
1H NMR spectra also show several coupled multiplets at δ 6.57–7.84 ppm for 1a-3a and 1b-3b typical for
the ring protons of L1–3 and 1. A peak observed at δ 11.76 ppm in LH1–3 characteristic of intramolecular
hydrogen bonded phenolic OH disappears in spectra of 1a-3a and 1b-3b indicating deprotonation of
phenolic proton, confirming coordination through phenolic oxygen [21]. A broad singlet at ~δ 2.69 ppm
observed in spectra of all complexes corresponds to CH2 protons of dppe. 31P NMR spectra of the CuII/RuII
and CdII/RuII complexes show a singlet at ~47 ppm, confirming trans geometry at ruthenium in which the
two dppe ligands occupy the equatorial plane with the Cl- and alkynyl group trans in axial positions [22].
Proposed molecular structures of the complexes are confirmed by ESI mass spectra. The formula-
tion of CuII/RuII and CdII/RuII complexes is assigned from the presence of molecular ion peak and other
prominent peaks in mass spectra. The mass spectra of 1a-3a and 1b-3b show that the molecular ion
peak is present in all the complexes at low abundance. The formation of CuII/RuII hybrid complexes is
clearly supported from the molecular ion peak at m/e 1306, 1385, and 1351 in 1a-3a, respectively, with
base peak at 1041; mass spectra of 1b-3b showed molecular ion peaks at m/e 1355, 1434, and 1400,
respectively, equal to theoretical molecular weight for CdII/RuII complexes. The peaks centered at m/z
1041 in 1a-3a and 1b-3b are due to a charged fragment ([NC5H4C≡CRu(dppe)2Cl)]+, obtained by the
loss of the Schiff base ligand and Cu or Cd ion from the organometallic moiety (1). A further loss of
pyridine acetylene ligand from the ruthenium center gives the intense group of charged ions centered
around m/z 957. The peaks at m/z 898 in 1a-3a are due to a singly charged species ([Ru(dppe)2]+. The

JOURNAL Of COORdINATION CHEMISTRy
7
Figure 2. tem image of as synthesized Cuii/ruii complexes.
CuII/RuII and CdII/RuII complexes also show prominent peaks due to elimination of Cl−, C6H5, Schiff base,
dppe, tropylium, iodide, CH=CH, etc. from the parent ion and subsequent fragment. The fragmentation
patterns of all the complexes are in general agreement with proposed chemical formulation. ESI mass
spectra of coordination organometallic complexes are quite complex with number of peaks due to the
presence of numerous ions containing isotopes. Complex 2b contains ruthenium, cadmium, bromine,
and chlorine atoms so the expected isotope pattern is complex. figure 3S Inset spectrum shows the
theoretical isotopic pattern of the expected molecular species (2b). figure 3S shows that the isotopic
profile for the acquired data closely matches that predicted by the isotope model. The peak at 1085
corresponded to fragment ions that have the characteristic isotopic distribution pattern of one bromine
and one chlorine (3b) at M, M + 2, M + 4 in the ratio 3:4:1. The ESI mass spectra of CuII/RuII and CdII/RuII
complexes also show the mutual location of bands as well as their ion composition and isotopic pattern
are specific for each complex. figure 1 provides a schematic drawing of the complexes.
figure 2 shows the representative TEM image of as synthesized CuII/RuII complexes. The TEM image
clearly indicates that complex nanoparticles are formed with well-arranged spheres. On the basis ofTEM
image the size of CuII/RuII hybrid complexes is ~60 nm. TEM image also shows well-dispersed spherical
nanoparticles without agglomeration.
3.2. Cyclic voltammetry
The electrochemical features of the bimetallic complexes were investigated in dMf containing 0.05 M
n-Bu4NClO4 as supporting electrolyte by cyclic voltammetry. All measurements were carried out in
10−3 M solutions at room temperature from +1.5 to −1.5 V with scan rate 100 mVs−1. The cyclic voltam-
metric (CV) data of the CuII/RuII and CdII/RuII complexes are summarized in table 1.
Table 1. electrochemical data of Cuii /ruii and Cdii/ruii complexes (1a-3a and 1b-3b).
CuI/CuII
RuII/RuIII
Epa(V)
Epc(V)
E1/2(V)
Epa(V)
Epc(V)
E1/2(V)
1a
2a
3a
1b
2b
3b
0.971
0.980
0.982
–
–
–
0.863
0.876
0.882
–
–
–
0.917
0.928
0.932
–
–
–
1.183
1.226
1.255
1.131
1.152
1.162
1.093
1.132
1.171
1.066
1.072
1.081
1.138
1.179
1.213
1.098
1.112
1.121
note: supporting electrolyte: n-Bu4nClo4 (0.05 m); complex: 0.001 m; solvent: dmf; E1/2 = ½ (Epa + Epc); scan rate: 100 mVs−1.

8
B. G. BHARATE ANd S. S. CHAVAN
Table 2. fluorescence spectral data of Cuii/ruii and Cdii/ruii complexes (1a-3a and 1b-3b).
Complex
Excitation (nm)
Emission (nm)
ϕ
1a
2a
3a
1b
2b
3b
342
345
348
354
355
357
447
451
454
459
465
477
0.037
0.038
0.041
0.042
0.046
0.047
Figure 3. emission spectra of 1a-3a.
Cyclic voltammetry studies 1a-3a reveal that the complexes undergo quasireversible oxidation
processes at 0.917–0.932 V assigned to CuI/CuII. Another oxidation process in 1a-3a at 1.138–1.213 V is
assigned to the RuII/RuIII couple. In 1b-3b only oxidation of RuII/RuIII couple is observed at 1.098–1.121 V.
Compared to 1 the oxidation of the RuII unit shifted more positive, indicating it is difficult to oxidize
upon coordination of MII unit which increases the electron density around MII [23, 24].
3.3. Thermogravimetric analyses
The thermal stabilities of CuII/RuII and CdII/RuII complexes were investigated by thermogravimetric
analyses (TGA). TGA were performed at a heating rate of 10 °C min−1 under flowing nitrogen to 800 °C.
TGA data suggest that 1a-3a are stable to 258 °C revealing the absence of either water or solvent. In
the temperature range of 259–350 °C, these complexes underwent complicated multiple weight loss
steps with total loss corresponding to Schiff base and pyridylacetyl ligands (obsd. 21.68 (1a), 26.41 (2a),
24.37 (3a) %; Calcd 22.29 (1a), 26.79 (2a), and 24.93 (3a) %). All the complexes collapse due to release
of dppe ligand along with Cl- per formula unit between 351 and 534 °C with an observed weight loss
of 64.37 (1a), 60.73 (2a), 62.08 (3a), respectively (Calcd 64.85 (1a), 61.09 (2a), and 62.59 (3a)%). for 1b-
3b, the decomposition stage with mass loss of 20.96 in 1b, 25.67 in 2b, and 23.69% in 3b correspond
to Schiff base and pyridyl acetyl ligand at 261–357, 268–365, and 263–351 °C, respectively (theoretical
mass loss: 21.48, 25.86, 24.04%). Another stage at 362–612, 370–597, and 355–619 °C with mass loss

JOURNAL Of COORdINATION CHEMISTRy
9
of 62.21, 58.74, and 60.15% may be assigned to decomposition of the remaining half of dppe ligand
which is in agreement with a calculated mass loss of 62.48 (1b), 58.98 (2b), and 60.43 (3b) %.
3.4. Fluorescence spectral studies
The photoluminescence properties of binuclear complexes and 1 and the effect of ligand substituents
on photophysical properties have been investigated. The emission spectra of all the CuII/RuII and CdII/
RuII complexes were recorded in dMf at room temperature as summarized in table 2 and the spectra
of the complexes are depicted in figures 3 and 4. 1a-3a show blue-green emission at ca. 447–454 nm
upon excitation with λex 342–348 nm. However, CdII-RuII complexes show emission at 459–477 nm for
1b-3b excited at 354–357. On comparing the emission maxima of heterobimetallic complexes and 1
(441 nm) a slight red shift is observed. These results are consistent with what we observed in absorption
spectra in which a red shift occurs in heterobimetallic complexes. Hence emission spectra also confirm
the formation of binuclear species leading to increased energy gap between ground state and excited
state. These results also confirm an emission origin predominantly not only due to π → π* intraligand
transition but also with some metal-ligand charge transfer (MLCT) character, which enhance the rigid-
ity of the ligands and thus reduces the loss of energy through radiationless decay of the intraligand
emission excited state [25, 26].
fluorescence quantum yields of all the complexes were measured by the integration sphere method
using quinine sulfate as a reference with known ФR. The area of emission spectrum was integrated using
the software available in the instrument and the quantum yield was calculated by using
ꢀS = AS/ARX (Abs)R∕(Abs)SX ꢀR
where ϕS and ϕR are the fluorescence quantum yield of sample and reference, respectively, AS and AR
are the area under the fluorescence spectra of the sample and reference, respectively, and (Abs)S and
(Abs)R are the respective optical densities of the sample and the reference solution at the wavelength of
Figure 4. emission spectra of 1b-3b.

10
B. G. BHARATE ANd S. S. CHAVAN
Table 3. measured shG values of Cuii /ruii and Cdii/ruii complexes (1a-3a and 1b-3b).
Complex
Efficiency (relative to urea)
1a
2a
3a
1b
2b
3b
0.16
0.18
0.19
0.19
0.21
0.25
excitation. All the complexes exhibit good quantum yields of 0.037–0.047 for 1a-3a and 1b-3b, slightly
higher than structurally related compounds reported [27–29].
3.5. Nonlinear optical properties of the complexes
The nonlinear optical properties of the CuII/RuII and CdII/RuII complexes have been studied by the Kurtz-
powder technique and second harmonic generation (SHG) efficiencies are given in table 3. The SHG
efficiency observed for CuII/RuII 1a-3a is 0.16–0.19 times that of urea. However, 1b-3b show SHG effi-
ciency 0.20–0.25 times that of urea. SHG efficiency clearly indicates that the second-order NLO response
of CdII/RuII complexes is a little larger than the CuII/RuII complexes. The SHG efficiency of 1 is compared
with the binuclear complexes, showing that binuclear complexes are two times more active. The best
value of SHG efficiency is reached for the CdII/RuII complex having a 5-nitro-2-(pyrrole-2-yl-methylidine)
aminophenol (L3) ligand.
4. Conclusion
The
heterobimetallic
complexes
[Cu(L1–3)(NC5H4C≡CRu(dppe)2Cl)]
(1a-3a)
[Cd(L1–3)
(NC5H4C≡CRu(dppe)2Cl)] (1b-3b) have been prepared and characterized. The electrochemical behavior
of the complexes indicates that the complexes exhibit a quasireversible redox process. TEM analyses
confirmed the formation of CuII/RuII hybrid nanomaterials with well-dispersed nanospheres of ~60 nm
size. According to the quantum yields and fluorescence spectra, the complexes have relatively good
fluorescence properties. The SHG efficiencies of the complexes were measured by the Kurtz-powder
technique, indicating that all the complexes are NLO active with good NLO response.
Acknowledgements
We gratefully acknowledge financial support from department of Science andTechnology (dST Ref. No. SR/fT/CS-004/2008),
New delhi, India. Council of Scientific and Industrial Research (CSIR), New delhi for awarding Senior Research fellowship
(SRf). We thank Prof. P. K. das, IPC department, IISc, Bangalore for providing NLO facility.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was financially supported by the department of Science and Technology, New delhi, India [grant number
dST Ref. number SR/fT/CS-004/2008]; and Council of scientific and Industrial Research (CSIR), New delhi [grant number
124183/2k11/1].
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