Impact of ligand substituents on the crystal structures, optical and conducting properties of phenylmercury(II) β-oxodithioester complexes

Article abstract of DOI:10.1016/j.jorganchem.2020.121532

New phenylmercury(II) complexes 1–5 with functionalized β-oxodithioester ligands, [PhHg(II) (β-oxodithioester)], β-oxodithioester = methyl-3-hydroxy-3-(4-pyridyl)-2-propenedithioate L1 1, methyl-3-hydroxy-3-(p-chlorophenyl)-2-propenedithioate L2 2, methyl

Full text of DOI:10.1016/j.jorganchem.2020.121532

Journal of Organometallic Chemistry 928 (2020) 121532
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Impact of ligand substituents on the crystal structures, optical and
conducting properties of phenylmercury(II) β-oxodithioester
complexes
Kavita Kumaria, Michael G.B. Drewb, Nanhai Singha,∗
a Department of Chemistry, Institute of Science, Banaras Hindu University, Varanasi 221005, India
b Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
New phenylmercury(II) complexes 1–5 with functionalized β-oxodithioester ligands, [PhHg(II) (β-
oxodithioester)], β-oxodithioester = methyl-3-hydroxy-3-(4-pyridyl)-2-propenedithioate L1 1, methyl-3-
hydroxy-3-(p-chlorophenyl)-2-propenedithioate L2 2, methyl-3-hydroxy-3-(naphthyl)-2-propenedithioate
Received 9 August 2020
Revised 12 September 2020
Accepted 14 September 2020
Available online 25 September 2020
L3 3, methyl-3-hydroxy-3-(9-anthracenyl)-2-propenedithioate L4
4
and methyl-3-hydroxy-3-(p-
fluorophenyl)-2-propenedithioate L5 5, were synthesized and characterized by elemental (C, H, N)
analysis, IR, UV-Vis., 1H and 13 C{1H} NMR spectroscopy. Their structures have been investigated by single
crystal X-ray diffraction. Linear two-coordinate geometry about the Hg atom, via ipso-C of the phenyl
group and by S15 atom of the β-oxodithioester ligands is revealed in all complexes. Intramolecular
Keywords:
Conductivity
Crystal structures
PhHg(II) β-oxodithioesters
Luminescent properties
˚
Hg···O bonding at 2.622(10)–2.813(6) A is present in all the complexes. In 1–3, the asymmetric unit
contains a single discrete molecule whereas complexes 4 and 5 contain two. Except for 4 having bulky
anthracene substituent, intriguing supramolecular networks are sustained through intermolecular metal
assisted Hg···S and Hg···N and Cl···Cl, Cl···π, S···S, C–H···S, C–H···F, C–H···π interactions in these
complexes. In 1 the pyridyl N on 4-position on the substituent is involved in Hg···N bonding interactions
˚
A generating a 2-D net-like polymeric structure. All the
on the neighboring molecule at 2.938(7)
complexes showed bright green luminescent emissions both in solution and solid phase. The complexes
(σrt values = 10−3–10−6 S cm−1) show semiconducting characteristics with Ea values = 0.14–0.64 eV.
The electronic and steric properties of the substituents on the dithioester unit significantly influence
their structures and properties.
© 2020 Elsevier B.V. All rights reserved.
1. Introduction
dithioester ligands have been reported [18,19] but their structural
investigations, study of properties and applications have gained lit-
There has been significant growth of interest in the coordina-
tion chemistry of organomercury(II) and mercury(II) compounds
not only to gain understanding concerning mercury-cysteine in-
teractions in biological processes which can lead to severe health
hazards causing damage to brain and endocrine system, environ-
mental pollution and possible chemical antidotes, but also because
of their intriguing structural chemistry and material properties
[1–7]. The chemistry of metal complexes including mercury
with 1,1-dithiolato ligands, such as dithiocarbamate, xanthate and
dithiophosphate containing identical S,S-donor atoms have been
widely explored because of their multifaceted chemistry and ap-
plications in diverse areas [8–17]. Metal complexes of related
tle attention [20–22] although in recent years some main group
and transition metal have been studied [20,21].
The developing interest in dithioester ligand chemistry is due
to the functionalization of substituents that may substantially give
rise to intriguing structures and modified physical properties. It
is therefore crucial to make changes to ligand substituents with
varied electronic and steric characteristics to map out the struc-
tures and properties of their complexes. With this in mind, in
this contribution we report on the syntheses, crystal structures,
luminescent and conducting properties of five new phenylmer-
cury(II) complexes with pyridyl 4(N), p-chlorophenyl, 2-naphthyl,
9-anthracenyl and p-fluorophenyl functionalized β-oxodithioester
ligands (Scheme 1). The important perspectives of pursuing this
work are: (i) unlike 1,1-dithio ligands with soft bidentate S,S-
donors, the β-oxodithioesters having both soft S and hard O donor
atoms may expand their bonding ability with a variety of hard
∗
Corresponding author.
E-mail address: nsingh@bhu.ac.in (N. Singh).
https://doi.org/10.1016/j.jorganchem.2020.121532
0022-328X/© 2020 Elsevier B.V. All rights reserved.

K. Kumari, M.G.B. Drew and N. Singh
Journal of Organometallic Chemistry 928 (2020) 121532
Scheme 1. The β-oxodithioester ligands used in the work.
and soft metal ions. Usually the O,S-coordination mode of the
β-oxodithioester ligands stabilize six-membered chelate ring in
comparison to strained four-membered chelate rings formed by
1,1-dithio ligands about the metal centre; (ii) the compounds of
mercury(II), with d10 electronic configuration do not feature lig-
and field bands and as a result their coordination numbers as
well as structures are not imposed by ligand field stabilization re-
quirements. The usual coordination numbers exhibited are 2 and
4 with linear/tetrahedral arrangements, however higher coordina-
tion numbers 3, 5 and 6 are also stabilized with weaker metal
assisted bonding interactions. In-spite of the strength of Hg−S
bond, the Hg···S and Hg···O interactions play crucial roles in the
organization of supramolecular motifs. The incorporation of sub-
stituents on the dithioester backbone with varied steric bulk and
different donor atoms N, Cl or F may induce secondary bond-
ing interactions and increase the dimensionality of the complexes;
(iii) the luminescent properties of divalent group 12 metal com-
plexes particularly with Zn and Cd [5b,5d,23–26] are well docu-
mented, however studies on mercury complexes are rather scant.
The more electronegative oxygen with small p-orbitals and less
electronegative sulfur with more diffused d-orbitals within the
molecules may modify the HOMO-LUMO gap and hence vary lumi-
nescent characteristics; and (iv) the sulfur rich planar metal com-
plexes exhibited interesting conducting properties in solid state
because of effective S···S intermolecular contacts [14–16]. The
non planar complexes of chalcogenocyanates though limited in
number, have also displayed interesting conducting characteristics
[27,28].
TROCHEM), 2-acetylnaphthalene, p-chloroacetophenone and p-
fluoroacetophenone (Avra) were procured and used as received.
Solvents were purified and distilled adopting standard procedures
[29]. Melting points of the complexes were measured in open cap-
illaries using a Gallenkamps apparatus and are uncorrected. The
experimental details dealing with the elemental analysis (C, H, N)
and recording of IR (as KBr pellets) are the same as described
earlier [21]. NMR (1H, 13C{1H}) spectra were recorded on a JEOL
ECZ500 MHz FT-NMR spectrometer in CDCl3 [21b]. Chemical shifts
were reported in ppm using TMS as internal standard. UV–Vis
absorption, and solution and solid phase photoluminescent spec-
tra were obtained at room temperature using Shimadzu UV-1800
and PerkinElmer LS-55 fluorescence spectrophotometer, respec-
tively. The pressed pellet conductivity of the complexes was mea-
sured on a Keithley 236 Source Measure Unit by using a conven-
tional two probe technique. X-ray powder diffraction data (PXRD)
were collected on a Brüker D8 diffractometer with Cu Kα radiation
˚
(λ = 1.541836 A) in the 2θ range 5–50°, with a scan speed and a
step size of 1° and 0.02° min−1 respectively.
2.2. Synthesis of ligands (HL1–HL5)
The ligands, methyl-3-hydroxy-3-(4-pyridine)-2-propenedith-
ioate HL1, methyl-3-hydroxy-3-(p-chlorophenyl)-2-propenedith-
ioate HL2, methyl-3-hydroxy-3-(2-naphthyl)-2-propenedithioate
HL3, methyl-3-hydroxy-3-(9-anthracenyl)-2-propenedithioate HL4
and methyl-3-hydroxy-3-(p-fluorophenyl)-2-propenedithioate HL5
were synthesized according to the procedure as reported ear-
lier [22,23]. To a solution of NaH (0.6 g, 25 mmol) dissolved in
DMF: n-hexane mixture (4:1; 20 mL) was added gradually 4-
acetylpyridine (1.21 g, 10.0 mmol) (for HL1), p-chloroacetophenone
(1.54 g, 10.0 mmol) (for HL2), 2-acetylnaphthalene (1.7 g, 10.0
mmol) (for HL3), 9-acetylanthracene (2.20 g, 10.0 mmol) (for HL4)
and p-fluoroacetophenone (1.38 g, 10.0 mmol) (for HL5) in DMF
(20 mL) separately. The reaction mixture was stirred for 1 h in
an ice bath under N2 atmosphere and a solution of dimethyl-
trithiocarbonate (TTC) (1.38 g, 10.0 mmol) was added slowly and
2. Experimental
2.1. Materials and methods
All experiments were carried out in air at ambient temperature
and pressure except the syntheses of ligands which were carried
out under N2 atmosphere. Reagent grade chemicals, PhHg(OAc)
(SD Fine Chemicals), 4-acetylpyridine, 9-acetylanthracene (SPEC-
2

K. Kumari, M.G.B. Drew and N. Singh
Journal of Organometallic Chemistry 928 (2020) 121532
Scheme 2. Synthetic methodolgy for the potassium salts KL1–KL5 and their corresponding complexes 1–5.
UV-Vis. (CH2Cl2, λmax (nm), ε (M−1 cm−1)): 270 (2.86 × 104), 330
(1.28 × 104).
the mixture was further stirred for 10 h at room temperature.
Excess NaH was neutralized by addition of 0.1 M HCl (50 mL),
and the product was extracted with dichloromethane (3 × 50 mL),
washed with brine solution and water, concentrated and dried
over anhydrous Na2SO4. The product thus obtained was purified
by silica gel (100-200 mesh) chromatography using n-hexane as
the eluent to collect crystalline yellow solids and characterized by
IR and NMR spectroscopy (Ligand characterization data, in S3).
2.3.2 [PhHg(L2)] 2: Yield: (0.42 g, 80%). M.pt. 158–161°C. Anal.
Calcd for C16 H13ClHgOS2 (521.42): C 36.85, H 2.51%. Found: C
36.64, H 2.64%. IR (KBr, cm−1): 1588 (νC=O), 1476 (νC=C), 1091
(νC-S). 1H NMR (500 MHz, CDCl3, ppm): δ 2.64 (s, 3H, –SCH3), 6.97
(s, 1H, –CH=C–), 7.30–7.89 (m, 9H, ArH). 13C{1H} NMR (125 MHz,
CDCl3, ppm): δ 19.23 (–SCH3), 114.82 (–CH=C–), 129.21−138.85
(Ar-C), 168.88 (–C=O), 185.86 (=C–S–). UV-Vis. (CH2Cl2, λmax (nm),
ε (M−1 cm−1)): 258 (1.03 × 104), 380 (2.77 × 104).
2.3. Synthesis of complexes (1-5)
2.3.3 [PhHg(L3)] 3: Yield: (0.44 g, 82%). M.pt. 140–143°C. Anal.
Calcd for C20H16 HgOS2 (537.04): C 44.73, H 3.00%. Found: C 44.51,
H 3.13%. IR (KBr, cm−1): 1597 (νC=O), 1475 (νC=C), 1124 (νC-S). 1H
NMR (500 MHz, CDCl3, ppm): δ 2.75 (s, 3H, –SCH3), 7.39 (1H, s,–
CH=C–), 7.49–8.50 (m, 12H, Ar–H). 13C{1H} NMR (125 MHz, CDCl3,
ppm): δ 18.98 (–SCH3), 115.34 (–CH=C–), 124.50–157.60 (Ar–C),
167.18 (–C=O), 186.85 (=C–S–). UV-Vis. (CH2Cl2, λmax (nm), ε (M−1
cm−1)): 245 (1.55 × 104), 394 (1.88 × 104).
For the synthesis of complexes, potassium salts of the ligands
(KL1–KL5) were generated by stirring a 10 mL acetone solution of
β-oxodithioesters HL1−HL5 (1 mmol) and solid K2CO3 (0.21 g, 1.5
mmol) for 4-5 h under reflux conditions. This was filtered off and
the solution was dried on a vacuum evaporator to yield yellow to
orange solids of the KL1–KL5.
To a stirred (10 mL) methanolic solution of KL1 (0.21 g, 1
mmol), KL2 (0.24 g, 1 mmol), KL3 (0.26 g, 1 mmol), KL4 (0.31 g,
1 mmol) or KL5 (0.22 g, 1 mmol) was slowly added a suspen-
sion of PhHg(CO2CH3) (0.336 g, 1mmol) in 10 mL methanol sep-
arately. Yellow precipitate was formed within a short while and
the reaction mixture was further stirred for 3 h at room temper-
ature (Scheme 2). The yellow solids thus formed were filtered off
and washed with methanol followed by diethyl ether. The yellow
crystals of complexes 1–5 were obtained by slow evaporation in
dichloromethane solution within 2-3 weeks.
2.3.4 [PhHg(L4)] 4: Yield: (0.46 g, 78%). M.pt. 146–149°C. Anal.
Calcd for C24H18 HgOS2 (587.09): C 49.10, H 3.09%. Found: C 48.87,
H 3.22%. IR (KBr, cm−1): 1590 (νC=O), 1463 (νC=C), 1133 (νC-S). 1H
NMR (500 MHz, CDCl3, ppm): δ 2.34 (s, 3H, –SCH3), 6.62 (1H, s,–
CH=C–), 7.18–8.40 (m, 14H, Ar–H). 13C{1H} NMR (125 MHz, CDCl3,
ppm): δ 19.01 (–SCH3), 121.19 (–CH=C–), 125.39–137.65 (Ar–C),
167.82 (–C=O), 193.66 (=C–S–). UV-Vis. (CH2Cl2, λmax (nm), ε (M−1
cm−1)): 255 (1.154 × 105), 350 (0.83 × 104), 370 (1.09 × 104), 386
(1.13 × 104).
2.3.5 [PhHg(L5)] 5: Yield: (0.42 g, 84%). M.pt. 120-123°C. Anal.
Calcd for C16 H13FHgOS2 (504.97): C 38.06, H 2.59%. Found: C 37.82,
H 2.71%. IR (KBr, cm−1): 1595 (νC=O), 1477 (νC=C), 1053 (νC-S). 1H
NMR (500 MHz, CDCl3, ppm): δ 2.61 (s, 3H, –SCH3), 6.95 (1H, s,–
CH=C–), 7.10–7.95 (m, 9H, Ar–H). 13C{1H} NMR (125 MHz, CDCl3,
ppm): δ 18.97 (–SCH3), 114.65 (–CH=C–), 115.60–166.29 (Ar–C),
167.69 (–C=O), 185.41 (=C–S–). UV-Vis. (CH2Cl2, λmax (nm), ε (M−1
cm−1)): 256 (1.61 × 104), 352 (2.41 × 104).
2.3.1 [PhHg(L1)] 1: Yield: (0.38 g, 79%). M.pt. 172–175°C. Anal.
Calcd for C15H13HgNOS2 (487.97): C 36.92, H 2.69, N 2.87%. Found:
C 36.72, H 2.80, N 3.05%. IR (KBr, cm−1): 1592 (νC=O), 1472 (νC=C),
1059 (νC-S). 1H NMR (500 MHz, CDCl3, ppm): δ 2.65 (s, 3H, –
SCH3), 6.94 (1H, s, –CH=C–), 7.69–8.77 (m, 4H, C5H4N), 7.30–7.44
(m, 5H, Ar–H). 13C{1H} NMR (125 MHz, CDCl3, ppm): δ 19.01 (–
SCH3), 113.84 (–CH=C–), 121.25, 146.72, 150.80 (C5H4N), 129.16,
129.20, 136.57, 137.77 (Ar–C), 172.35 (–C=O), 185.01 (=C–S–).
3

K. Kumari, M.G.B. Drew and N. Singh
Journal of Organometallic Chemistry 928 (2020) 121532
2.4. X-ray crystal structure determination
sent in the complexes 1–5. The signal for vinylic proton in the free
ligands (δ 6.83−7.10 ppm) and their corresponding complexes (δ
6.62−7.39 ppm) remains almost unchanged. The position of the
methyl protons of –SCH3 in the complexes revealed no noticeable
shift and appeared in the range δ 2.34−2.75 ppm. In the 13C{1H}
NMR spectra, the resonances for the C−OH carbon are observed at
Single crystals of 1–5 were obtained by slow evaporation of so-
lutions of the compound in CH2Cl2. Single crystal X-ray diffrac-
tion data for complexes 1–4 were collected on an Oxford X-
calibur CCD diffractometer at 150 K using Mo Kα radiation and
5 on a Bruker D8 Quest SCM X-ray diffractometer at 100 K.
Data analysis was carried out using the CrysAlis program [30]. All
structures were solved using direct methods with the SHELXS-97
[31] and refined on F2 by full matrix least-squares method using
SHELXL2016-6 [32]. The non-hydrogen atoms were refined with
anisotropic thermal parameters. The hydrogen atoms bonded to
carbon were included in geometric positions and given thermal
parameters equivalent to 1.2 times those of the atom to which
they were attached. The –SMe group in complex 3 was disor-
dered over two positions. Crystals of both complexes 2 and 3 were
twinned. Diagrams for the complexes were prepared using OLEX2
[33] and Mercury [34] software. Crystal data for 1–5 were de-
posited at the Cambridge Crystallographic Data Centre with ref-
erence numbers CCDC 1532701, 1570469, 1570468, 2004456 and
2004457.
2.5. Theoretical calculations
Single point calculations were carried out using the Gaussian 03
program [35]. Structures were carried out using the B3LYP density
functional together with basis sets LANL2DZ for Hg, 6-31+G∗ for S,
N and O and 6-31G for C and H. Starting models were taken from
the crystal structures but with hydrogen atoms given normalised
positions via GaussView [36].
3. Results and discussion
3.1. Synthesis and characterization
Treatment of a methanolic solution of PhHg(OAc) with the
potassium salts of the β-oxodithioester ligands, KL1–KL5 in an
equimolar ratio, resulted in the formation of air- and moisture sta-
ble light yellow solids of PhHg(II) β-oxodithioester complexes 1–5
in good yields (Scheme 2). They are insoluble in common organic
solvents such as ethanol, methanol, acetone, acetonitrile, benzene
but are soluble in dichloromethane, DMF and DMSO. Complexes
were characterized by elemental analysis, spectroscopy (IR, UV-Vis.,
1H and 13C{1H}) and their solid state structures have been deter-
mined by single crystal X-ray diffraction. Homogeneity of the bulk
samples of 1−5 was confirmed by comparing the observed PXRD
patterns with the respective simulated powder patterns observed
from the single crystal data. The experimental and simulated PXRD
patterns are well in agreement indicating the phase purity of the
bulk samples (Fig. S1). Complexes 1–5 exhibit bright green lumi-
nescence characteristics in solution and solid phases. The semicon-
ducting behaviour of the complexes was investigated by pressed
pellet electrical conductivity measurements.
3.2. Spectroscopic Studies
In the IR spectra, the characteristic νC−OH, νC=S and νC=C vi-
brations of uncoordinated β-oxodithioester ligands appear in the
regions 1060−1165, 1217–1245 and 1579−1601 cm−1 respectively.
In complexes 1–5 these vibrations occur at 1588−1597, 1053−1133
and 1463−1477 cm−1 respectively. A perceptible decrease in the
νC−S frequency in the complexes as compared to the ligands in-
dicates the coordination via S–atom of the –SCSMe group of the
β-oxodithioester ligands.
In the 1H NMR spectra, the ligands HL1–HL5 show the –OH
Fig. 1. ORTEP diagrams of the complexes 1–5 with displacement ellipsoids at 30%
probability. H atoms have been omitted for clarity.
proton resonances in the δ 14.78−15.37 ppm range which are ab-
4

K. Kumari, M.G.B. Drew and N. Singh
Journal of Organometallic Chemistry 928 (2020) 121532
Fig. 1. Continued
δ 165.30−170.18 ppm and δ 167.18−172.35 ppm in the uncoordi-
nated ligands and their complexes, respectively. The vinylic carbon
of the ligands at δ 107.53−115.17 ppm is slightly downfield shifted
at δ 113.84−121.19 ppm in the complexes. The –C=S carbon at δ
216.62−219.27 ppm in the free ligands shows an upfield shift and
is observed at δ 185.01–193.66 ppm in the complexes indicating
metal–sulfur bonding. This indicates that the keto form of the β-
oxodithioester ligand is stabilized in these complexes [20] (crystal
structures vide infra).
gles, respectively, at 102.0(3), 75.1(1) and 174.8(2)° for 1, 101.7(10),
79.2(4) and 178.2(11)° for 2, 99.5(8), 77.8(6) and 177.2(9)°for
3, 106.4(5), 79.1(3) and 174.2(4) for 4A; 105.2(5), 80.5(3) and
174.3(4)° for 4B, 101.2(2), 79.7(1) and 178.5(2) for 5A; 99.9(2),
79.4(1) and 178.1(2)° for 5B.
In 1, the distant pyridyl
N in the 4-position of the β-
oxodithioester ligand L1 of a neighbouring molecule is oriented
to Hg atom forming intermolecular Hg···N34$2 contacts [2, 4b–e]
($2=-1+x, ½-y, -1/2+z) at a somewhat longer distance of 2.938(7)
˚
A which is well within the range of intermolecular Hg–N contacts
[39]. Simultaneously the S15$1 atom in a different adjacent ligand
3.3. Crystal structures
molecule ($1=x, 1/2-y, -1/2+z) is attached to Hg atom forming in-
˚
termolecular Hg···S contacts at 3.230(2) A leading to a 2-D net-
Single crystals of 1–5 were grown by slow evaporation of a
CH2Cl2 solution. Crystallographic data and structure refinement pa-
rameters for all crystals are presented in Table 1 and the selected
bond lengths and bond angles are listed in Table 2. ORTEP dia-
grams of the complexes with displacement ellipsoids at 30% prob-
ability are shown in Fig. 1. In 1, 2 and 3, the asymmetric unit con-
tains a single discrete molecule whereas complexes 4 and 5 con-
tain two independent molecules.
like polymeric structure (Fig. 2). By comparison in the reported
[20] analogous PhHg(II) β-oxodithioester complex the pyridyl N
in the 3-position forms 1-D coordination polymeric structure. The
sulfur atom of the −SMe group is not involved in the forma-
tion of Hg···S contacts due to its poor electron donating capabil-
ity. Considering the metal-assisted intra- and intermolecular sec-
ondary bonding interactions, the Hg atom can be considered to
be five-co-ordinate (Fig. 2b) with a geometry intermediate be-
tween square pyramidal and trigonal bipyramidal with a τ value
of 0.497 [40]. The observed bond angles are N34$2−Hg1−O11
145.0(2)o, O11−Hg1−S15$1 127.7(1)o, S15$1−Hg1−N34$2 76.9(1)o
and S15$1−Hg1−C21 92.7(1)o. It is worth noting that in this com-
In 1–5, two-coordinate geometry about the Hg atom is de-
fined [37] by the ipso-C of the phenyl ring at 2.036(18)-2.084(13)
˚
˚
A and S15 of the β-oxodithioester at 2.350(5)-2.386(5) A with
the C21–Hg1–S15 angles of 174.2(4)-178.5(3)° indicating small but
significant deviations from linearity. The Hg1···O11 distances of
˚
plex the carbonyl oxygen is bonded to Hg atom at 2.813(6) A, a
˚
2.622(10)-2.813(6) A in 1–5 are somewhat longer but significantly
distance significantly longer than those found in 2−5 but still sig-
˚
less than the sum of van der Waals radii [38] of 3.23 A. This
˚
nificantly smaller than the sum of van der Waals radii of 3.23 A
weaker bond establishes a distorted T-shaped structure about the
Hg atom with C21–Hg1–O11, S15–Hg1–O11 and C21–Hg1–S15 an-
[30]. This bond lengthening can presumably be attributed to the
5

K. Kumari, M.G.B. Drew and N. Singh
Journal of Organometallic Chemistry 928 (2020) 121532
Table 1
Crystallographic data and refinement parameters for complexes 1–5.
Compound
1
C
2
3
4
5
Chemical formula
Formula weight
Crystal system
Space group
15H13HgNOS2
C16H13ClHgOS2
521.42
C20H16HgOS2
537.04
C24H18HgOS2
587.09
C16H13FHgOS2
504.97
487.97
monoclinic
P21/c
monoclinic
P21
monoclinic
P21
monoclinic
P21/c
monoclinic
P21/c
˚
a (A)
10.1483(7)
21.8960(13)
7.2581(4)
110.451(7)
1511.15(17)
4
11.5285(8)
5.3034(3)
13.1702(9)
95.889(7)
800.98(9)
2
12.6105(19)
5.4072(6)
12.9648(18)
96.201(14)
878.9(2)
2
8.2006(6)
17.493(2)
28.7380(18)
90.012(6)
4122.6(6)
8
25.8140(13)
5.2441(3)
23.1032(11)
101.356(2)
3066.3(3)
8
˚
b (A)
˚
c (A)
β(o)
3
˚
V (A )
Z
ρcalc (g cm−3
)
2.145
2.162
2.029
1.892
2.188
T (K)
150(2)
150(2)
150(2)
150(2)
100(2)
μ(Mo Kα) (mm−1
)
10.455
10.029
8.997
7.681
10.316
F(000)
920
492
512
2256
1904
Reflections collected
Independent reflns
Reflections with I > 2σ(I)
Final indices [I > 2σ(I)] R1a, wR2
R1[a], wR2[b][all data]
GOF
9867
5517
4154
20593
46736
4210
2286
1931
11166
7558
3173
2016
1504
5931
6291
b
0.0535, 0.0988
0.0767, 0.1080
1.005
0.0589, 0.1583
0.0675, 0.1647
1.019
0.0795, 0.1797
0.1018, 0.1919
1.058
0.0829, 0.1678
0.1629, 0.2024
0.935
0.0331, 0.0837
0.0469, 0.0932
1.070
3
˚
Max., min. residual electron density (e/ A )
3.303, -2.389
3.444, -1.345
3.288, -1.855
2.661, -3.297
1.759, -1.549
a
R1 = ꢀ ǀǀFoǀ - ǀFcǀǀ/ ꢀǀFoǀ.
b
2
2
R2 = {[ꢀw(Fo – Fc2)/ ꢀw(Fo2)2]}1/2, w= 1/[σ2(Fo2) + (xP)2], where P = (Fo + 2Fc2)/3.
Table 2
Bond lengths and bond angles in complexes 1–5.
˚
Bond Lengths (A)
1
2
3
4A
4B
5A
5B
Hg1-O11
Hg1-S15
Hg1-C21
Hg1-S15$1
O11-C12
C12-C13
C13-C14
C14-S15
C14-S16
2.813(6)
2.377(2)
2.059(7)
3.230(2)
1.241(9)
1.426(11)
1.359(10)
1.746(8)
1.750(9)
2.674(12)
2.386(5)
2.077(15)
3.326(11)
1.23(2)
2.73(2)
2.380(7)
2.084(13)
3.285(17)
1.19(3)
1.43(4)
1.43(4)
1.70(3)
1.80(2)
2.688(10)
2.350(5)
2.036(18)
n/a∗
2.622(10)
2.371(5)
2.060(18)
n/a∗
2.645(4)
2.3802(14)
2.071(6)
3.296(1)
1.248(7)
1.425(8)
1.365(8)
1.732(6)
1.760(6)
2.640(4)
2.3752(14)
2.081(5)
3.3236(14)
1.242(7)
1.430(8)
1.367(8)
1.737(5)
1.762(6)
1.211(18)
1.43(2)
1.273(18)
1.438(18)
1.37(2)
1.46(3)
1.41(3)
1.34(2)
1.73(2)
1.737(15)
1.754(14)
1.734(15)
1.743(16)
1.77(2)
Bond Angles (o)
1
2
3
4A
4B
5A
5B
C21-Hg1-S15
C21-Hg1-O11
O11-Hg1-S15
Hg1-O11-C12
O11-C12-C13
C12-C13-C14
C13-C14-S15
Hg1-S15-C14
S15-C14-S16
174.75(19)
102.0(3)
75.07(13)
110.3(5)
125.8(7)
128.4(7)
129.4(7)
106.9(3)
107.9(4)
178.2(11)
101.7(10)
79.2(4)
177.2(9)
99.5(8)
77.7(6)
117.9(18)
127(3)
174.2(4)
106.4(5)
79.1(3)
174.3(4)
105.2(5)
80.5(3)
178.49(16)
101.16(18)
79.67(10)
119.0(4)
178.06(13)
99.90(17)
79.43(10)
119.2(4)
123.8(6)
128.9(5)
131.5(5)
106.0(2)
116.3(3)
119.4(16)
126(2)
120.3(10)
124.0(17)
129.6(16)
129.9(11)
103.8(6)
105.8(8)
118.6(8)
125.9(15)
128.7(16)
129.8(12)
106.0(7)
108.9(9)
124.0(6)
125.4(19)
133.3(17)
105.0(6)
115.9(11)
124(3)
129.2(6)
134(2)
131.6(5)
103.8(9)
120.4(15)
105.60(19)
116.6(3)
Symmetry element $1 In 1 -1+x, ½-y, -½+z; in 2 1-x, -1/2+y, 2-z; in 3 1-x, y+1/2, 1-z; in 5A 1-x, y+1/2, ½-z; in 5B
2-x, y+1/2, 3/2-z
∗
no sulfur atom in the equatorial plane
orientation of the pyridyl group in the polymeric network which
forces the carbonyl oxygen slightly away from the metal. In order
to test the importance of the two intermolecular interactions de-
scribed above, single point calculations were carried out on two
molecules so associated and E(dimer) – 2∗E(monomer) showed fa-
vorable interactions. That calculated involving the N34$2 interac-
tion (coordinates x, y, z and -1+x, ½-y, -1/2+z) gave an energy dif-
ference of 4.50 kcalmol−1and that for the S15$1 interaction (coor-
oxodithioester ligand L2 and L3 at 2.077(15), 2.076(9), 2.084(13)
˚
˚
A; and 2.674(12), 2.653(7), 2.726(12) A respectively. Also the metal
centre is weakly bonded to S15$1 atoms in adjacent molecules at
˚
˚
3.326(11) A, $1 = 1-x, y-1/2, 2-z in 2; and 3.285(17) A $1 = 1-x,
½+y, 1-z in 3 resulting in the formation of 1-D linear zig-zag poly-
meric chain along a screw axis (Figs. 3 and 4). The significance of
this weak interaction between the metal and S15$1 can be evalu-
ated by the fact that it is present in all three structures as well as
in complex 5 despite the structures having very different unit cells
(vide supra). Therefore a rare distorted square planar coordination
environment particularly with a d10 metal centre is established in
these complexes. In 2 the four donor atoms show an r.m.s. devi-
dinates x, y, z and x, 1/2-y, -1/2+z) 3.57 kcalmol−1
.
Likewise in complexes 2 and 3 derived from the p-chlorophenyl
and 2-naphthyl β-oxodithioester ligand L2 and L3 respectively,
the Hg atom is three coordinate T-shaped being bonded to the
˚ ˚
ation of 0.169 A with the metal atom 0.134(10) A from the plane.
ipso-carbon C21 of
a
phenyl ring, S15 and O11 atoms of β-
6

K. Kumari, M.G.B. Drew and N. Singh
Journal of Organometallic Chemistry 928 (2020) 121532
˚
˚
Fig. 2. (a) 2-D polymeric chain motif in 1 via intermolecular Hg-S15$1 (3.230(2) A) and Hg-N34$2 (2.938(7) A) bonding interactions. (b) The distorted five-coordinate
˚
environment of the metal centre in 1. Distances are reported in A.
Fig. 3. (a) 1-D polymeric chain view of 2 showing intermolecular Hg···S, Cl···Cl and Cl···π bonding interactions. (b) Bond angles about mercury atom showing distorted
˚
square planar coordination. Distances are reported in A and angles in degree (°).
7

K. Kumari, M.G.B. Drew and N. Singh
Journal of Organometallic Chemistry 928 (2020) 121532
Fig. 4. 1-D polymeric chain view of 3 showing intermolecular Hg···S bonding interactions. (b) Bond angles about mercury atom showing distorted square planar coordination.
˚
Distances are reported in A and angles in degree (°).
Fig. 5. 1-D polymeric chain motif network in 4 formed through C–H···π interactions. Hydrogen atoms not involved in interactions are omitted.
8

K. Kumari, M.G.B. Drew and N. Singh
Journal of Organometallic Chemistry 928 (2020) 121532
Fig. 6. Supramolecular structure of 5 sustained by weak intermolecular Hg···S, S···S, S···H and non-covalent C-H···F interactions. Hydrogen atoms not involved in interactions
˚
are omitted. Distances are reported in A.
˚
together with B molecules. The metal atoms can therefore best be
considered as three-coordinate.
Equivalent value is 0.116, 0.122(10) A in 3. In the crystal structure
of 2, the supramolecular structure is stabilized by a chain of weak
Cl34···Cl34$1 ($1 = -x, ½+y, 1-z and -x, -1/2+y, 1-z) along the y
Many C–H···π interactions are found in 4 (Fig. 5) involving the
˚
˚
˚
anthracene rings with distances (d) of 3.51 A involving H36B and
axis at (3.34(1) A) and Cl34···π$2 ($2 = x, -1+y, z) (3.60 A) inter-
actions (Fig. 3).
centre of gravity (Cg) of ring containing atoms C39A–C44A inclu-
˚
˚
sive, d 3.28 A involving H38B and Cg C31A–C44A, d 3.07 A in-
Unlike 1−3, the crystal structures of 4 and 5 contain two
independent molecules in the asymmetric unit (Fig. 1). In 4,
there are only slight variations between the dimensions in the A
and B molecules, thus the Hg1−S15A, Hg2−S15B and Hg1−O11A,
˚
volving H40B and Cg C32A–C37A, d 3.59 A involving H36A and Cg
˚
C39B–C44B, d 3.29 A involving H38A and Cg C31B–C44B, d 2.91
˚
˚
A involving H40A and Cg C32B–C37B, d 2.55 A involving H17B and
˚
˚
˚
˚
Cg C39A–C44A, d 3.08 A involving H17C and Cg C31A–C44A, d 3.54
Hg2−O11B distances are 2.350(5) A, 2.371(5) A and 2.688(10) A,
˚
˚
˚
A involving H17D and Cg C31B–C44B and d 2.61 A involving H17E
and Cg C32B–C37B.
2.622(10) A respectively. However the structure is unique, very
different from those found in 1, 2, 3 and 5. The steric bulk of
anthracene group has prevented any prominent weaker bonding
interactions to organize the supramolecular networks in 4 and
so there is no polymer formation. There are intermolecular weak
By contrast in 5 there are shorter Hg···S contacts comparable
to those found in 2 and 3 which form similar but distinct inde-
pendent polymers for molecules A and B both along a screw axis.
˚
˚
Distances are Hg1···S15A$1 ($1 = 1-x, ½+y, ½-z) at 3.296(1) A and
Hg···S contacts Hg1···S15B (1+x,y,z) at 3.529(7) A and Hg2···S16A
˚
˚
Hg2···S15B$1 ($1 = 2-x, ½+y, 3/2-z) at 3.324(1) A. Similar to those
at 3.419(7) A but these are longer than the shortest intermolecular
structures, the r.m.s. deviations from the square planes are 0.153
Hg···S contacts found in 2 and 3 and also in very different orien-
tations as they are not positioned in the equatorial plane. And it
will be noted that these interactions involve A molecules mixed
˚
˚
and 0.138 A with the metal atoms 0.125(2), 0.172(2) A from the
planes in A and B respectively.
9

K. Kumari, M.G.B. Drew and N. Singh
Journal of Organometallic Chemistry 928 (2020) 121532
Fig. 7. (a) Electronic absorption spectra of complexes 1–3, 5 (b) and complex 4 in CH2Cl2 solution and (c) solid state absorption spectra of 1–5 in Nujol mull.
The smaller p-fluorophenyl substituent on the β-oxodithioester
3.4. Optical properties
backbone allowed prominent S···S interactions, namely
˚
A
S16A···S16A (1-x, 4-y, 1-z) of 3.354(1)
and S16B···S16B (2-
Absorption and Emission Spectra. The UV-Vis. absorption
spectra of 1–5 in CH2Cl2 and solid as Nujol mull are presented in
fig. 7. In solution the absorption bands near 250-270 nm (ε = 1.01–
11.54 × 104 M−1 cm−1) and 350-400 nm (ε = 1.09–2.80 × 104 M−1
cm−1) are mostly ligand centered and are assigned to intraligand
charge transfer (ILCT) and slightly metal perturbed ILCT transitions
respectively [3,5b–d] (Fig 7a, b). In solid as Nujol mull, they exhibit
absorption bands near 250-280 nm and 340-440 nm (Fig. 7c); the
features of the spectra in two media are almost similar apart from
the differences in intensity of the absorptions and slight variations
in their positions. This reveals that the structures of the complexes
are virtually persistent in solution.
˚
x, 1-y, 2-z) 3.530(2) A, which connect the polymers formed along
the screw axes described above via centres of symmetry to form
two dimensional separate A and B polymers as shown in Fig 6.
˚
Additional C–H···S and C–H···F interactions at 2.99 A, and 2.64
˚
A help to stabilize the supramolecular architecture. Among the
˚
structures other than 5 the shortest S···S distances are >=3.95 A.
There are no significant Hg···Hg intermolecular distances in the
˚
five structures with the shortest distance of 4.108(1) A significantly
˚
higher than the sum of van der Waals radi of 3.46 A [38]. The crys-
tal structures of 1, 2 and 4 are also stabilized by weak C–H···S in-
teractions. (Fig. S2)
The C12−O11 carbonyl bond lengths in the range
All the complexes displayed bright green luminescent emissions
in solution and solid phases when irradiated in the UV-Vis. light.
Upon excitation at 260 nm in CH2Cl2 solution, 1−3 and 5 dis-
˚
1.19(3)−1.273(18) A in 1−5 are consistent with the partial dou-
ble bonds. The C13−C14 bond lengths for 1−5 in the range
max
˚
1.34(2)−1.44(4)
A
show distinct double bond character. The
˚
play an unstructured medium broad emission bands near λemis
C14−S15 distances of 1.70(3)−1.746(8) A and the slightly longer
330−420 nm with a Stokes shift of 100−140 nm (Fig. 8a) arising
˚
C14–S16 distances of 1.743(16)−1.80(2) A are in the range for the
from the ILCT state. When excited at 350−360 nm, they show an
max
C–S single bond lengths. Thus some delocalization of electron den-
sity is observed over the six-membered chelate ring comprising of
O11, C12, C13, C14, S15 and Hg1 atoms in these complexes (Fig. 1).
unstructured broad emission bands at around λemis
400 nm,
with a relatively smaller Stokes shift of 50 nm (Fig. 8b). Interest-
ingly complex 4 upon excitation at 260, 350, 370 and 386 nm ex-
10

K. Kumari, M.G.B. Drew and N. Singh
Journal of Organometallic Chemistry 928 (2020) 121532
Fig. 8. Emission spectra of complexes 1–3, 5 at (a) λex = 260 nm; (b) λex = 350 nm, (c) and complex 4 at λex = 260 nm, 350 nm, 370 nm, 386 nm in CH2Cl2 solution (d)
max
Solid phase emission spectra of 1–5 at room temperature, λem
at 390 nm.
hibits structured emission bands at 410, 430 and 460 nm (Fig. 8c)
in solution characteristic of the anthracene group, obeying Kasha’s
rule; [41,42] the red shifted emissions in this compound may be
attributed to enhanced delocalization provided by the anthracene
group on the β-oxodithioester ligand L4. Upon excitation at 350
nm in the solid, 1−5 exhibit perceptible red shifted strong emis-
sion band at ~500 nm accompanied with a shoulder at 530 nm
in comparison to their solution spectra (Fig. 8d). The prominent
luminescent properties of all the complexes may be attributed to
their almost identical luminescence chromophores as well as to the
supramolecular architectures sustained via various metal assisted
Hg···N, Hg···S and other weaker Cl···Cl, C–H···F and S···S inter-
molecular interactions in the solid state.
3.5. Pressed pellet conductivity
The temperature dependence of the pressed pellet electrical
conductivities of the powdered complexes have been measured
by conventional two-probe technique using a Keithley 236 elec-
tometer in the temperature range 303-373 K (Fig. 9). The pel-
Fig. 9. Temperature dependent pressed pellet conductivity plots for complexes 1, 2
and 5.
11

K. Kumari, M.G.B. Drew and N. Singh
Journal of Organometallic Chemistry 928 (2020) 121532
lets were made at a pressure of 2.0 × 105 kN m−2 with tablet
size 13 mm in diameter and 0.5 mm thickness and contacts on
the pellet surfaces were made using silver paint. Complexes 1, 2
and 5 with σrt values in the 10−3-10−6 S cm−1 range are weakly
conducting. Their lower conductivities may be attributed to the
lack of S···S intermolecular contacts in the solid state (vide supra
in the crystal structures) which is an important prerequisite for
their higher conductivities [14]. They show behaviour of semicon-
ductors in the measured temperature range of 303–373 K with
Ea= 0.14-0.64 eV as their conductivities correlate with change in
temperature.
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oxodithioester ligands have been synthesized and well char-
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the Hg atom, bound by the S15 atom of the β-oxodithioester
ligand and C21 atom of the aromatic ring, the O atom of the
ligand is weakly attached to the metal centre. In complex 1 the
Hg atom is also weakly bonded to pyridyl N on 4-position on
the β-oxodithioester in an adjacent molecule. Simultaneously
the S atom on a different adjacent molecule is also attached to
Hg atom forming a 2-D net-like polymeric structure. In these
complexes varied supramolecular structures are sustained via
Hg···N, Hg···S, C−H···π, Cl···Cl, Cl···π, S···S, C−H···S and C−H···F
secondary interactions. All the complexes show bright green
luminescent emissions in solution and solid phases. The stronger
luminescent characteristics of 4 are attributed to the presence
of higher conjugation in anthracene moieties on the dithioester
unit. Temperature dependent pressed pellet conductivity mea-
surements indicate semiconducting behaviour of the complexes.
This study demonstrates that the electronic and steric properties
of the substituents on the β-oxodithioester ligands backbone
may substantially influence the solid state structures, bonding
interactions, formation of supramolecular architectures as well
as luminescent and conducting properties of the organomercury
dithioester complexes and their possible applications as functional
materials.
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Declaration of Competing Interest
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The authors declare that they have no known competing finan-
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NS and KK gratefully acknowledge financial support from the
University Grants Commission (UGC), New Delhi for the award of
BSR Faculty Fellow (ref No. F. 18-1/2011(BSR) 30 Dec 2016) and
CSIR-SRF fellowship respectively. We are also thankful to the De-
partment of Chemistry, Institute of Science, Banaras Hindu Univer-
sity, UGC CAS-II for infrastructural and instrumentation facilities.
M.G.B. Drew acknowledges EPSRC (UK) and the University of Read-
ing for funds for the X-Calibur system.
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