A family of salamo-type trinuclear Co(II) and Ni(II) complexes: Structural characterization, Hirshfeld surface analysis and fluorescent properties

Article abstract of DOI:10.1016/j.poly.2021.115267

Three trinuclear complexes, [{CoL(MeOH)(μ-OAc)}₂Co] (1), [{CoL(EtOH)(μ-OAc)}₂Co]·2CH₃CH₂OH (2) and [{NiL(MeOH)(μ-OAc)}₂Ni]·2CH₃OH (3) have been successfully synthesized by wet-chemical meth

Full text of DOI:10.1016/j.poly.2021.115267

Polyhedron 204 (2021) 115267
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Polyhedron
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A family of salamo-type trinuclear Co(II) and Ni(II) complexes: Structural
characterization, Hirshfeld surface analysis and fluorescent properties
⇑
Peng Li, Shi-Zhen Li, Yu-Xin Wei, Wen Kui Dong
School of Chemistry and Chemical Engineering, Lanzhou Jiaotong University, Lanzhou 730070, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Three trinuclear complexes, [{CoL(MeOH)(
l
-OAc)}2Co] (1), [{CoL(EtOH)(
l
-OAc)}2Co]Á2CH3CH2OH (2) and
Received 20 March 2021
Accepted 11 May 2021
Available online 17 May 2021
[{NiL(MeOH)(
l
-OAc)}2Ni]Á2CH3OH (3) have been successfully synthesized by wet-chemical method
using asymmetric salamo-based polydentate chelating ligand (H2L) with transition metal(II) acetate
(Co(OAc)2Á4H2O or Ni(OAc)2Á4H2O). The ligand H2L with N2O2 coordination cavity can accommodate tran-
sition metals, at the same time, the oxygen atoms of the phenolic hydroxyl groups can bridge the metal
atoms to obtain muiltnuclear metal complexes. There are inversion centers in complexes 1–3 and all M
(II) atoms possess six-coordinated distorted octahedral geometries. Complexes 1 and 3 are further assem-
bled into extended two-dimensional supramolecular via intermolecular interactions, but complex 2
forms three-dimensional supramolecular structure. The interactions were quantitatively determined
by Hirshfeld surfaces analyses. Significantly, complexes 1–3 have been characterized by elemental anal-
yses, IR spectra, UV–Vis spectroscopy and X-ray crystallography analyses. Fluorescence properties were
also investigated.
Keywords:
Salen-type ligand
Complex
Crystal structure
Hirshfeld surface analysis
Fluorescence property
Ó 2021 Elsevier Ltd. All rights reserved.
1. Introduction
significantly affect the electron density distribution of ligands
and control the reversible reaction of imine bonds, we can use
Coordination chemistry has been active in various fields of
chemistry, and has become an important branch of chemistry [1].
Over the years, salen-bases played an important role as chelating
ligands in the coordination chemistry of main group, transition
metals and rare earth [2]. The complex units formed by salen
and its analogues are the basic building blocks for supramolecular
structures and coordination polymers, which is an important part
of the diversity of the complexes [3]. The tetradentate salen-base
ligands and their transition metal complexes have been exten-
sively studied in the fields of catalytic reactions [4], optical mate-
rials and biochemistry [5], and continue to expand their research
fields in breadth and depth. Salen and its related N2O2 polydentate
chelating ligands are usually prepared by gently heating the mixed
solution of diamines and salicylaldehyde and its derivatives [6].
However, due to the instability of imine bond, which is not possible
obtain a single compound with two or more N2O2-donor cavities
[7]. Through the years, in the field of coordination chemistry, a
new type of salen-based analogue, salamo-based compounds (R-
CH = NAO-(CH2)nAOAN = CH-R) have been developed [8]. Because
the strong electronegativity of oxygen atoms, which can
unstable and stable building blocks to describe the compounds
based on salen- and salamo-based compounds [9]. Through coordi-
nation-driven self-assembly, various 3d [10], 3d-s [11], 3d-4f [12]
homometal-multinuclear, hetermetal-multinuclear complexes
and coordination polymers have been developed based on sym-
metric and asymmetric salamo-based ligands. Nowadays, the syn-
thesis of salamo-based polydentate chelating ligands [13],
complexes [14] and molecular probes [15] with excellent proper-
ties and specific structures, as well as the exploration of potential
applications in various fields, have become part of the field of coor-
dination chemistry. Nabeshima’s group has done a lot of excellent
researches on salamo-based ligands and their corresponding
macrocyclic complexes, chiral complexes and the selective intro-
duction of different metal ions in different cavities [16].
Here, we designed and synthesized a new asymmetric polyden-
tate chelating ligand H2L with N2O2 donor and three M(II) com-
plexes 1–3 [3f–3i]. Through coordination-driven self-assembly
and quantitative analysis of Hirshfeld surface, the interactions
between complex units have been studied, and the fluorescence
properties have also been explored.
⇑
Corresponding author.
E-mail address: dongwk@126.com (W.K. Dong).
https://doi.org/10.1016/j.poly.2021.115267
0277-5387/Ó 2021 Elsevier Ltd. All rights reserved.

P. Li, Shi-Zhen Li, Yu-Xin Wei et al.
2. Experimental section
Polyhedron 204 (2021) 115267
4.33; N, 11.03%. 1H NMR (500 MHz, CDCl3): d 10.66 (s, 1H), 9.90 (s,
1H), 8.31 (s, 1H), 8.22–8.19 (m, 1H), 8.19–8.16 (m, 2H), 7.08 (d,
J = 3.7 Hz, 1H), 7.07 (d, J = 3.2 Hz, 1H), 6.52 (d, J = 2.4 Hz, 1H),
6.50 (dd, J = 8.5, 2.5 Hz, 1H), 4.55 (dt, J = 6.3, 3.6 Hz, 2H), 4.49
(dt, J = 4.0, 3.6 Hz, 2H), 3.84 (s, 3H).
2.1. Materials and instrumentation
5-Nitrosalicylic aldehyde (98%), 2-hydroxy-4-methoxyben-
zaldehyde (98%), N-Hydroxyphthalimide (98%) and 1,2-dibro-
moethane (99%) were purchased from Meryer and used without
further purification, hydrazine hydrate (ꢀ80%) was purchased from
YUMEI and used without further purification. The solvents and
reagents were analytical grade reagents. C, H and N analyses were
performed via a GmbH VarioEL V3.00 automatic elemental analy-
ses instrument. 1H NMR spectra were recorded using a Bruker
AVANCE DRX-400 spectrometer (Bruker AVANCE, Billerica, MA,
USA). Melting points were made via microscopic melting point
instrument made in Beijing Tektronix Instruments Limited Com-
pany. FT-IR spectra were gained via a VERTEX70 FT-IR spectropho-
tometer, with samples prepared as KBr (4000–400 cmÀ1) pellets.
UV–Vis absorption spectra were obtained via a Shimadzu UV-
2550 spectrometer. X-ray single crystal structures were carried
out on a Bruker D8 Venture diffractometer. Fluorescence spectrum
were measured via an F-7000 FL spectrophotometer.
2.3. Synthesis of complex 1
To 2 mL of CHCl3/ CH3CN mixed solution (v/v = 1: 1) of H2L
(3.75 mg, 0.01 mmol) was added 4 mL of MeOH solution of Co
(OAc)2Á4H2O (2.90 mg, 0.01 mmol), which immediately turned to
light brown. The brown block-shaped single crystals suitable for
X-ray crystallographic analysis was obtained by kept undisturbed
crystallization at room temperature with evaporating part of the
solution. Finally, washed with methanol, and then dried at ambient
temperature. Yield: 45%, based on Co(OAc)2Á4H2O. Anal. Calc. for
C
40H44Co3N6O20 (%): C, 43.45; H, 4.01; Co, 15.99; N, 7.60. Found:
C, 43.85; H, 3.82; Co, 15.36; N, 7.33.
2.4. Synthesis of complex 2
The same method as complex 1 was used. To 2 mL of CHCl3/
CH3CN mixed solution (v/v = 1: 1) of H2L (3.75 mg, 0.01 mmol)
was added 4 mL of EtOH solution of Co(OAc)2Á4H2O (2.90 mg,
0.01 mmol). Yield: 43%, based on Co(OAc)2Á4H2O. Anal. Calc. for
2.2. Synthesis and characterization of H2L
The synthesis of 1,2-bis(aminooxy)ethane is shown in scheme
1, please refer to the original literatures [8].
C46H60Co3N6O22 (%): C, 45.07; H, 4.93; Co, 14.42; N, 6.86. Found:
C, 45.36; H, 4.82; Co, 14.09; N, 6.44.
The synthetic routes of 2-[O-(1-ethyloxyamide)]oxime-4-nitro-
phenol and H2L are shown in scheme 1. 2-[O-(1-Ethyloxyamide)]
oxime-4-nitrophenol was prepared by the solution of 5-nitrosali-
cylic aldehyde (3 mmol, 506.1 mg) in ethanol (60 mL) was added
to a solution of 1,2-bis(aminooxy)ethane (6 mmol, 552.36 mg) in
ethanol (10 mL), the mixed solution was reacted for 4 h. The solu-
tion was concentrated in vacuo and the residue was purified by col-
2.5. Synthesis of complex 3
Ni(OAc)2Á4H2O (2.50 mg, 0.01 mmol) was dissolved in 3 mL of
ethanol, a solution of H2L (3.80 mg, 0.01 mmol) in CHCl3/CH3CN
mixed solution (v/v = 1: 1) was added to it, which immediately
turned to light green. Finally, the harvested green crystals were
washed with ethanol. Yield: 49%, based on Ni(OAc)2Á4H2O. Anal.
Calc. for C42H52N6Ni3O22 (%): C, 43.15; H, 4.48; Ni, 15.06; N, 7.19.
Found: C, 43.46; H, 4.12; Ni, 14.79; N, 6.94.
umn
chromatography
(SiO2,
dichloromethane
/ethyl
acetate
=
15:1), 2-[O-(1-ethyloxyamide)]oxime-4-nitrophenol
was collected by concentrated in vacuo. Yield: 41.1%. Anal. Calc.
for C9H11N3O5: C, 44.82; H, 4.60; N, 17.42. Found: C, 44.75; H,
4.65; N, 17.26%. 1H NMR (500 MHz, CDCl3): d 10.73 (s, 1H), 8.27
(s, 1H), 8.18 (dd, J = 9.1, 2.7 Hz, 1H), 8.14 (d, J = 2.7 Hz, 1H), 7.07
(d, J = 9.1 Hz, 1H), 5.54 (s, 2H), 4.44–4.41 (m, 2H), 4.01–3.98 (m,
2H).
2.6. Crystal structure determination
X-ray diffraction data of complexes 1–3 were collected on a
The ligand H2L was synthesized by the rection of 2-[O-(1-ethy-
loxyamide)]oxime-4-nitrophenol (241.1 mg, 1.0 mmol) in ethanol
(10 mL) with 2-hydroxy-4-methoxybenzaldehyde (152.1 mg,
1.0 mmol) in ethanol (10 mL). The solutions were stirred for 1 h.
Light pink precipitates were filtered, washed by a small amount
of ethanol and dried in vacuo. Yield: 78.6%. m. p.: 131–132 ℃ .Anal.
Calc. for C17H17N3O7: C, 54.40; H, 4.57; N, 11.20. Found: C, 54.95; H,
Bruker D8 Venture diffractometer with graphite-monochroma-
tized Mo-Ka radiation (k = 0.71073 Å). Complexes cooled in a
nitrogen gas cryostream to 173 K. The complexes structures were
solved by intrinsic phasing using the SHELXT [17], refinement
was performed in Olex2 with SHELXL-2018 by least-squares min-
imization against F2 [18a,18b]. Data were corrected for absorption
effects using the empirical multi-scan method (SADABS) [18c]. The
Scheme 1. Synthetic routes to 1,2-bis(aminooxy)ethane and the ligand H2L.
2

P. Li, Shi-Zhen Li, Yu-Xin Wei et al.
Polyhedron 204 (2021) 115267
nonhydrogen atoms were refined with anisotropic thermal param-
eters. All the hydrogen atoms were geometrically fixed and
allowed to refine using a riding model. Complex 1 has high positive
value of 1.41 e.A-3 in the final difference map, which is next to Co1
of complex 1. For structures containing heavy atoms, the peak/val-
ley maximums are usually larger, and these residual peaks are usu-
ally in the range of about 60–120 pm (0.6–1.2 Å) from the heavy
atoms. If the atomic number of the heavy atom is Z, these electron
density peaks or valleys can be considered reasonable in the range
of 0.1Z Â 10-6 e pmÀ3 ( 0.1Z eÅÀ3). The experimental details for
the structural determination are presented in Table 1. Selected
bond lengths (Å) and angles (°) for complexes 1–3 are presented
in Table 2.
frequencies, which indicates that the M(II) atoms are coordinated
with the N atoms of the C@N groups [10b]. Moreover, the Ar-O
stretching vibration band of ligand is observed at approximately
1285 cmÀ1
1213 cmÀ1
,
but complexes 1–3 appear at 1215, 1217 and
,
obviously shifted to lower frequencies, which
indicated that the M(II) atoms are coordinated with the O atoms
of the aromatic rings [12b]. At the same time, in order to
distinguish the MÀN and MÀO bonds, complexes infrared
spectrum have been carried out a careful study, the stretching
vibration bands appeared at 556, 583 and 562 cmÀ1 in the M(II)
complexes could be attributed to m(Cu–N) bonds, meanwhile, the
bands appeared at 478, 472, and 479 cmÀ1 were indicated
O) bonds [12d].
m(Cu–
3.1.2. UV–Vis spectroscopy
3. Results and discussion
The UV–Vis spectroscopy of the ligand and complexes 1–3 were
recorded at ambient temperature, which was dissolved in ethanol
with the concentration were 1 Â 10-5 mol/L. As shown in Fig. 2a,
three successive peaks at ca. 231, 273 and 304 nm were observable.
The absorption peaks at 231 and 273 nm could be attributed to the
3.1. Spectral investigation
3.1.1. IR spectra
The infrared spectra of the ligand H2L and its trinuclear com-
plexes were recorded in the range of 400–4000 cmÀ1 (Fig. 1). The
OAH stretching vibration band of the ligand was observed at
3425 cmÀ1 [9a], this band was disappeared in the IR spectra of
complexes 1–3, which is indicative of the fact that the phenolic
OH groups of H2L have been deprotonized and coordinated to the
Co(II) or Ni(II) atoms [12c]. Besides, absorption bands at about
3428, 3426 and 3426 cmÀ1 in complexes 1–3 could be ascribed
to the –OH groups of existed methanol or ethanol molecules,
respectively, which are also confirmed with the X-ray
crystallography analyses [10a]. The C@N groups of the ligand
p
-
p
* charges transition of aromatic rings [10a], and the later peak
at 304 nm could be identified as * charges transition of C@N
p-p
groups [13a]. Compared with the UV–Vis absorption peaks of the
ligand, the spectrums of complexes changed obviously (Fig. 2b).
The titration curves are given in Fig. 2c and Fig. 2d. The titration
curves of complexes 1 and 2 are given in Fig. 2c, compared with the
free ligand H2L (1 Â 10-5 mol/L), with the concentration of Co2+
(1 Â 10-3 mol/L) increase gradually, two new peaks have been dis-
covered at about 247 and 363 nm, but absorption peaks of ligand at
231 and 273 nm disappear, which indicted Co2+ ions have coordi-
nation with L2- units. Significantly, when the concentration of Co2+
ions reach 1.5 equivalents, the absorption intensity of the UV–Vis
absorption spectrums become stable, which indicated the stoi-
chiometry of Co2+ and H2L is 1.5 : 1 and consistent with X-ray crys-
have an obvious stretching vibration band at about 1608 cmÀ1
,
but in the complexes 1–3, the stretching vibration bands of C@N
appears at about 1603, 1607 and 1606 cmÀ1 and shifted to low
Table 1
Crystallographic data and refinement parameters for complexes 1, 2 and 3.
Complex
1
2
3
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimension
a (Å)
C
40H44Co3N6O20
C46H60Co3N6O22
1225.79
173.0
0.71073
triclinic
P-1
C42H52 N6Ni3O22
1169.02
173.0
0.71073
triclinic
P-1
1105.60
173.0
0.71073
monoclinic
P21/n
10.7988(7)
15.3763(11)
13.3942(10)
90
95.184(3)
90
2215.0(3)
2
1.658
8.9588(3)
10.9065(4)
14.2696(5)
70.6270(10)
79.8900(10)
76.3070(10)
1270.76(8)
1
10.4177(3)
10.8117(3)
10.9671(4)
101.2700(10)
100.7990(10)
94.0630(10)
1182.56(6)
1
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (g Á cmÀ3
)
1.602
1.057
1.642
1.273
l
(mmÀ1
)
1.200
F(000)
1134.0
635.0
606.0
Crystal size (mm)
h range (°)
0.16 Â 0.14 Â 0.13
0.21 Â 0.19 Â 0.17
0.19 Â 0.17 Â 0.14
4.622 to 53.644
5.328 to 53.626
4.852 to 53.47
Index ranges
À13 ꢁ h ꢁ 13,À17 ꢁ k ꢁ 17,À20 ꢁ l ꢁ 20 À11 ꢁ h ꢁ 11,À18 ꢁ k ꢁ 18,À19 ꢁ l ꢁ 19 À13 ꢁ h ꢁ 13,À15 ꢁ k ꢁ 15,À17 ꢁ l ꢁ 17
À19 ꢁ k ꢁ 19
À16 ꢁ l ꢁ 16
26,304
À13 ꢁ k ꢁ 13
À18 ꢁ l ꢁ 18
23,613
À13 ꢁ k ꢁ 13
À13 ꢁ l ꢁ 13
14,395
Reflections collected
Independent reflection
Completeness to (%) (h)
Data/restraints/parameters
4709 [Rint = 0.0792]
99.3
4709/1/320
5411 [Rint = 0.0583]
99.4
5411/9/367
0.0357, 0.0913
5021 [Rint = 0.0317]
99.8
5021/4/339
0.0319, 0.0720
Final R1, wR2 indices [I > 2r (I)] 0.0624, 0.1569
(I)]
2
r
R1, wR2 indices (all data)
0.0730, 0.1656
1.055
1.41/-0.98
0.0485, 0.0968
1.034
0.58/-0.53
0.0404, 0.0771
1.066
0.37/ À0.45
GOF
D
3
qmax,min (e Å–
)
3

P. Li, Shi-Zhen Li, Yu-Xin Wei et al.
Polyhedron 204 (2021) 115267
Table 2
Selected bond lengths (Å) and angles (°) for complexes 1–3.
Complex 1
Complex 2
Complex 3
Co1-O1
2.080(3)
Co1-O1
2.0460(15)
Ni1-O1
2.0225(15)
Co1-N2
Co1-N3
Co1-O6
Co1-O9
Co1-O8
Co2-O1
Co2-O6
Co2-O10
2.160(3)
2.122(3)
2.042(3)
2.059(3)
2.168(3)
2.133(3)
2.107(3)
2.049(3)
84.86(12)
166.62(12)
88.49(11)
83.48(12)
107.50(13)
87.91(12)
86.35(12)
164.60(12)
86.35(12)
93.75(11)
90.53(11)
93.11(11)
92.60(12)
91.43(12)
175.62(11)
180.0
Co1-N2
Co1-N3
Co1-O6
Co1-O9
Co1-O8
Co2-O1
Co2-O6
Co2-O10
2.1216(19)
2.058(2)
2.0438(15)
2.0638(16)
2.1932(18)
2.1535(15)
2.1222(15)
2.0337(15)
86.19(7)
167.04(8)
85.85(7)
85.41(7)
100.79(8)
84.17(9)
82.15(6)
168.16(7)
90.23(7)
89.05(6)
91.61(6)
95.50(6)
94.13(7)
94.87(8)
178.84(6)
180.0
Ni1-N2
Ni1-N3
Ni1-O6
Ni1-O9
Ni1-O8
Ni2-O1
Ni2-O6
Ni2-O10
2.0605(19)
2.0277(19)
2.0153(15)
2.0313(16)
2.0994(16)
2.1434(14)
2.0640(15)
2.0578(15)
88.35(7)
168.02(7)
86.27(6)
85.01(7)
99.90(8)
85.82(7)
81.30(6)
169.59(7)
90.95(7)
87.32(6)
95.38(6)
93.02(6)
92.13(7)
95.31(7)
177.07(7)
180.0
O1-Co1-N2
O1-Co1-N3
O1-Co1-O8
N2-Co1-O8
N3-Co1-N2
N3-Co1-O8
O6-Co1-O1
O6-Co1-N2
O6-Co1-N3
O6-Co1-O9
O6-Co1-O8
O9-Co1-O1
O9-Co1-N2
O9-Co1-N3
O9-Co1-O8
O1-Co2-O1#1
O6#1-Co2-O1
O6-Co2-O1
O6-Co2-O6#1
O10#1-Co2-O1
O10-Co2-O1
O10-Co2-O1#1
O10-Co2-O6
O10#1-Co2-O6
O10-Co2-O10#1
O1-Co1-N2
O1-Co1-N3
O1-Co1-O8
N2-Co1-O8
N3-Co1-N2
N3-Co1-O8
O6-Co1-O1
O6-Co1-N2
O6-Co1-N3
O6-Co1-O9
O6-Co1-O8
O9-Co1-O1
O9-Co1-N2
O9-Co1-N3
O9-Co1-O8
O1-Co2-O1#1
O6#1-Co2-O1
O6-Co2-O1
O6-Co2-O6#1
O10#1-Co2-O1
O10-Co2-O1
O10-Co2-O1#1
O10-Co2-O6
O10#1-Co2-O6
O10-Co2-O10#1
O1-Ni1-N2
O1-Ni1- N3
O1-Ni1- O8
N2-Ni1- O8
N3-Ni-N2
N3-Ni- O8
O6-Ni- O1
O6-Ni-N2
O6-Ni1-N3
O6-Ni1-O9
O6-Ni1-O8
O9-Ni1-O1
O9-Ni1-N2
O9-Ni1-N3
O9-Ni1-O8
O1-Ni2-O1#1
O6#1-Ni2- O1
O6-Ni2-O1
O6-Ni2-O6#1
O10#1-Ni2-O1
O10-Ni2-O1
O10-Ni2-O1#1
O10-Ni2-O6
O10#1-Ni2-O6
O10-Ni2-O10#1
101.89(10)
78.11(10)
180.0
92.05(11)
87.95(11)
92.05(11)
89.15(11)
90.84(11)
180.0
102.13(6)
77.87(6)
180.0
91.95(6)
88.41(6)
91.95(6)
88.01(6)
91.99(6)
180
102.64(6)
77.36(6)
180.00
91.86(6)
88.14(6)
91.86(6)
89.15(6)
90.49(6)
180.00(5)
#1
Symmetry code:
= 1-X, 1-Y, 1-Z.
tallographic analysis [11]. The titration curves of complex 3 is sim-
ilar to that of the former two (Fig. 2d), with the concentration of
Ni2+ (1 Â 10-3 mol/L) increase gradually, the 273 and 340 nm
absorption peaks of the free ligand gradually decrease and disap-
pear, and new absorption peaks appear at 252 and 374 nm, which
indicates that Ni2+ ions have coordinated with L2- units and affect
the charge transfer transition [12d]. Moreover, the absorption peak
of complex 3 at 239 nm is red-shifted by 8 nm compared with the
free ligand at 231 nm.
3.2. Description of the crystal structures
3.2.1. The crystal structure and supramolecular interactions of
complex 1
Complex 1 possesses inversion center and crystallizes in the
monoclinic crystal system (Fig. 3a), the crystal structure analysis
shows that complex 1 is homo-trinuclear complex and the formula
is [{CoL(MeOH)(
metal atoms, the
l
-OAc)}2Co]. Two ligand units (L)2- package three
l
-OAc-1 of the counter anions bridge two adja-
cent metal Co(II) atoms, and the terminal Co(II) atoms are coordi-
nated with the solvent molecules at axially available position, so
that all Co(II) atoms are six-coordinated (Fig. 3b). Co(II) atom
(Co2) is located in the O6 coordination cavity, the equatorial sites
around the Co2 occupied by the donor atoms O1, O6, O1#1 and
O6#1 of the ligand (L)2- units, the axial positions are the oxygen
atoms (O10 and O10#1) of the -OAc- counter anions. The terminal
l
Co(II) atoms (Co1) is located in the N2O4 cavity, N3, N7, O6 and O1
atoms come from N2O2 cavity to form equatorial plane, as well as,
the axial positions are occupied by the oxygen atoms of solvent
molecules (O8) and counter ions (O9), respectively. The trinuclear
Co(II) complex reported by the Datta group, through the
l
-N-3
anion to connect the metal Co(II) atoms to form a trinuclear Co
(II) complex [3f]. In 2019, the Andruh group reported a novel
trinuclear Co(II) complex constructed from Mannich-schiff-base
ligands [3g], there are different from that reported in this article.
In order to better explore the stacking trend of complexes,
intramolecular and intermolecular interactions have been studied.
Each complex unit have three intramolecular hydrogen bonds (C9-
HABÁÁÁO9, C2-H2ÁÁÁO10#1 and C13-H13ÁÁÁO10#1) (Fig. 3c). At the
same time, two intermolecular hydrogen bonds (O8#1-H8#1ÁÁÁO3#2
and C8-H8AÁÁÁO2#3) and two
p -
-related interactions (N1#2-O3#2
Fig. 1. IR spectra of H2L and its corresponding complexes 1–3 (cmÀ1).
4

P. Li, Shi-Zhen Li, Yu-Xin Wei et al.
Polyhedron 204 (2021) 115267
Fig. 2. (a) UV–vis spectrum of H2L (1 Â 10-5 M). (b) UV–vis spectra of complexes 1–3 (1 Â 10-5 M). (c) The changes in H2L (1 Â 10-5 M) upon addition of Co2+ (1 Â 10-3 M).
Inset: the absorbance at 363 nm varies with the interaction of [Co2+]/[H2L]. (d) The changes in H2L (1 Â 10-5 M) upon addition of Ni2+. Inset: the absorbance at 361 nm varies
with the interaction of [Ni2+]/[H2L].
Fig. 3. (a) Molecule structure of complex 1, ellipsoids are shown at the 30%
#1
probability level for reasons of clarity, symmetry code:
Coordination polyhedrons for Co(Ⅱ) atoms, symmetry code:
View of the intramolecular hydrogen bonds, symmetry code:
Hydrogen atoms are omitted for clarity.
= 1-x, 1-y, 1-z. (b)
#1
= 1-x, 1-y, 1-z. (c)
#1
= 1-x, 1-y, 1-z.
Fig. 4. View of the two-dimensional supramolecular structure of complex 1.
Intermolecular hydrogen bonds (O8#1-H8#1ÁÁÁO3#2 and C8-H8AÁÁÁO2#3
) and p-
related interactions (N1#2-O3#2ÁÁÁCg1#1 and C9#8-H9A#8ÁÁÁCg2, Cg1 are the centroids
of atoms C1/C2/C3/C4/C5/C6. Cg2 is the centroids of atoms C11/C12/C13/C14/C15/
ÁÁÁCg1#1 and C9#8-H9A#8ÁÁÁCg2) coordinate the complex units to
form two-dimensional supramolecular structure [1f,2g,24]
(Fig. 4). From the supramolecular structure of complex 1, we can
know that the oxygen atom of nitro group plays a key role in it.
Putative hydrogen bond interactions and geometrical parameters
C16.) of complex 1, symmetry code: #1 = 1-x, 1-y, 1-z; #2 = 1-x, 1-y, -z; #3 = -1 + x, y,
#8
z;
= -x, 1-y, 1-z. Hydrogen atoms are omitted for clarity.
plex 2 are different from that of complex 1, and there are crys-
talline solvent molecules at the same time (Fig. 5a, 5b). The
oxygen atoms of oxime group (O5, N3 and C10) are disordered
unequally over two different positions (O5 and O5A, 0.617(6) and
0.383(6)), which are allowed for during refinement [10a].
for the
p-related interactions of complexes 1–3 are shown in
Table 3 and Table 4, respectively.
3.2.2. The crystal structure and supramolecular interactions of
complex 2
Complex 2 possesses inversion center and crystallizes in the tri-
clinic crystal system, the formula is [{CoL(EtOH)(
2CH3CH2OH. Compared with complex 1, the coordination solvent
molecules at the axial position of the terminal Co(II) atoms of com-
In the structure of complex 2, four intramolecular hydrogen-
bondings (C2-H2ÁÁÁO10#1, C8-H8AÁÁÁO9, C13-H13ÁÁÁO1#1 and C18-
l
-OAc)}2Co]Á
H18AÁÁÁO10#1
) and one intramolecular p-related interactions
(C19-H19CÁÁÁCg1) were found, which plays a vital role in the struc-
tural stability of the complex unit (Fig. 5c). Simultaneously, one
5

P. Li, Shi-Zhen Li, Yu-Xin Wei et al.
Polyhedron 204 (2021) 115267
Table 3
Putative hydrogen bond interactions (Å) for complexes 1–3.
Complex 1
D–XÁÁÁA
d(D–X)
0.83(3)
0.99
0.95
0.99
d(XÁÁÁA)
1.96(3)
2.46
2.51
2.49
d(DÁÁÁA)
2.749(4)
3.335(5)
3.199(5)
3.297(6)
3.242(5)
\D–XÁÁÁA
158(6)
148
129
138
Symmetry code
1-x, 1-y, -z
O8#1-H8#1ÁÁÁO3#2
C9-H9ABÁÁÁO9
C2-H2ÁÁÁO10#1
C8-H8AÁÁÁO2#3
C13-H13ÁÁÁO10#1
Complex 2
1-x, 1-y, 1-z
À1 + x, y, z
1-x, 1-y, 1-z
0.95
2.57
128
D–XÁÁÁA
d(D–X)
0.88(3)
0.84
0.99
0.95
0.99
0.95
0.95
0.99
d(XÁÁÁA)
1.94(3)
2.18
2.56
2.55
2.29
2.60
2.54
2.39
d(DÁÁÁA)
2.801(4)
3.002(4)
3.221(4)
3.208(3)
3.225(3)
3.367(3)
3.329(4)
3.379(3)
3.335(5)
\D–XÁÁÁA
168(2)
168
124
126
158
138
140
178
Symmetry code
1-x, 1-y, 1-z
-x, 2-y, 1-z
1-x, 1-y, 2-z
1-x, 1-y, 1-z
O8-H8ÁÁÁO11#1
O11#4-H11#4ÁÁÁO7
C9-H9AAÁÁÁO3#5
C2-H2ÁÁÁO10#1
C8-H8AÁÁÁO9
C13-H13ÁÁÁO1#1
C15-H15ÁÁÁO11#4
C18-H18AÁÁÁO10#1
C22#6-H22B#6ÁÁÁO2
Complex 3
1-x, 1-y, 1-z
-x, 2-y, 1-z
1-x, 1-y, 1-z
x, 1 + y, z
0.99
2.57
134
D–XÁÁÁA
d(D–X)
0.84
0.838
0.95
0.99
0.99
d(XÁÁÁA)
1.89
1.91
2.56
2.10
2.44
2.47
2.44
d(DÁÁÁA)
2.587
2.732
3.259(3)
3.259(3)
3.328(3)
3.282(3)
3.379(4)
\D–XÁÁÁA
140
168
131
158
148
144
160
Symmetry code
O8-H8ÁÁÁO11
O11-H11ÁÁÁO10#1
O2-H2ÁÁÁO10#1
C8-H8AÁÁÁO9
1-x, 1-y, 1-z
1-x, 1-y, 1-z
C9#10-H9B#10ÁÁÁO7#1
C13-H13ÁÁÁO1#1
C20-H20CÁÁÁO11#5
-x, 1-y, 1-z
1-x, 1-y,1-z
1-x, 1-y, 2-z
0.95
0.98
#1
#2
#3
#4
#5
#6
#7
symmetry codes:
= 1-x, 1-y, 1-z;
= 1-x, 1-y, -z;
= -1 + x, y, z;
= -x, 2-y, 1-z;
= 1-x, 1-y, 2-z;
= x, 1 + y, z;
= x, 1-y, 1-z.
Table 4
Geometrical parameters for the
p-related interactions for complexes.
Complex 1
D-O/HÁÁÁA
D-O/H
1.249(5)
0.990
O/HÁÁÁA
DÁÁÁA
\D-O/HÁÁÁA
107.3(3)
127
Symmetry code
1-x, 1-y, -z
-x, 1-y, 1-z
N1#2-O3#2ÁÁÁCg1#1
C9#8-H9A#8ÁÁÁCg2
Complex 2
3.617(4)
2.95
4.163(5)
3.634(5)
D- HÁÁÁA
D- H
0.990
0.980
HÁÁÁA
2.86
2.93
DÁÁÁA
\D- HÁÁÁA
159
151
Symmetry code
1-x, 2-y, 1-z
C9-H9ABÁÁÁCg2#9
C19-H19CÁÁÁCg1
Complex 3
3.801(3)
3.819(3)
D- HÁÁÁA
D- H
HÁÁÁA
DÁÁÁA
\D- HÁÁÁA
158
133
Symmetry code
C21-H21AÁÁÁCg2
0.980
0.980
Rca
2.96
3.598(3)
3.649(3)
R2vc
C21-H21BÁÁÁCg1#5
2.91
1-x, 1-y, 2-z
Symmetry code
-x,1-y,1-z
p
ÁÁÁ
p
R1vb
a
Cg2#10ÁÁÁCg2#1
4.2228(13)
À3.3752(9)
À3.3752(9)
0.02(10)
Cg1 is the centroids of the (C1-C6) rings, Cg2 is the centroids of the (C11-C16) rings. a Centroid distance between Cg I (Cg2#10) and Cg J (Cg2#1). b Vertical distance from ring
centroid Cg 2#10 to ring Cg 2#1
.
c Vertical distance from ring centroid Cg 2#1 to ring Cg 2#10
.
a
= dihedral angle between planes Cg2#10 and Cg2#1. Symmetry codes: #1 = 1-x, 1-
#2
#8
#9
#10
y, 1-z;
= 1-x, 1-y, -z;
= -x, 1-y, 1-z;
= 1-x, 2-y, 1-z;
= -x, 1-y, 1-z.
intermolecular
p
-related interaction (C9-H9ABÁÁÁCg2#9) (Fig. 6)
trinuclear Ni(II) structure reported by the Liu group in 2017,
through the
-PhCOO- ions to connect the metal Ni(II) atoms to
form a new trinuclear Ni(II) complex [3i], there are different
coordinate with five intermolecular hydrogen-bondings (O8-
H8ÁÁÁO11#1, O11#4-H11#4ÁÁÁO7, C9-H9AAÁÁÁO3#5, C15-H15ÁÁÁO11#4
and C22#6-H22B#6ÁÁÁO2) to form three-dimensional infinite
supramolecular structure [1f,2g,24] (Fig. 7). Putative hydrogen
bond interactions and geometrical parameters for the
interactions of complexes 1–3 are shown in Table 3 and Table 4,
l
from that reported in this article.
By analyzing the intramolecular and intermolecular interac-
tions, we found that there is a significant difference between com-
plex 3 and the former two. Three intramolecular hydrogen bonds
(C2-H2ÁÁÁO10#1, C8-H8AÁÁÁO9 and C13-H13ÁÁÁO1#1) (Fig. 8c) were
found in complex units, which is helpful to the unique structure
of the complex. At the same time, four intermolecular hydrogen
bonds (O8-H8ÁÁÁO11, O11-H11ÁÁÁO10#1, C9#10-H9B#10ÁÁÁO7#1 and
p-related
respectively.
3.2.3. The crystal structure and supramolecular interactions of
complex 3
Complex 3 possesses inversion center and crystallizes in the tri-
clinic crystal system, the formula is [{NiL(MeOH)(
2CH3OH. The structure of complex 3 is similar to the former two
(Fig. 8a, 8b). Ghosh group reported a trinuclear Ni(II) complex,
the axial positions of Ni(II) atom in the center are coordination
H2O molecules, and the NCS- ions coordinated in the axial positions
of the terminal Ni(II) atoms are used as the counter-anion [3h]. The
C20-H20CÁÁÁO11#5) (Fig. 9) coordinate with
p-related interactions
(C21-H21BÁÁÁCg1#5, C21-H21AÁÁÁCg2 and Cg2#10ÁÁÁCg2#1) [1f,2g,24]
(Fig. 10) to form two-dimensional infinite supramolecular
structure. Through 2D fingerprints of quantitative analysis,
complex 3 has more CÁÁÁ C interactions, which is consistent with
the supramolecular structures of the complexes [19a]. Putative
hydrogen bond interactions and geometrical parameters for the
l
-OAc)}2Ni]Á
6

P. Li, Shi-Zhen Li, Yu-Xin Wei et al.
Polyhedron 204 (2021) 115267
Fig. 5. (a) Molecule structure of complex 2, ellipsoids are shown at the 30%
#1
Fig. 8. (a) Molecule structure of complex 3, ellipsoids are shown at the 30%
probability level for reasons of clarity, symmetry code:
Coordination polyhedrons for Co(Ⅱ) atoms, symmetry code:
= 1-x, 1-y, 1-z. (b)
= 1-x, 1-y, 1-z. (c)
#1
#1
probability level for reasons of clarity, symmetry code:
Coordination polyhedrons for Ni(II) atoms, symmetry code:
View of the intramolecular hydrogen bonds. Symmetry code:
Hydrogen atoms and solvent molecules are omitted for clarity.
= 1-x, 1-y, 1-z. (b)
#1
= 1-x, 1-y, 1-z. (c)
View of the intramolecular hydrogen bonds and C19-H19CÁÁÁCg1 interactions (Cg1
#1
#1
= 1-x, 1-y, 1-z.
are the centroids of atoms C1/C2/C3/C4/C5/C6.), symmetry code:
= 1-x, 1-y, 1-z.
The disordered positions O atoms of O5 only show the more populated position for
clarity. Hydrogen atoms and solvent molecules are omitted for clarity.
p-related interactions of complexes 1–3 are shown in Table 3 and
Table 4, respectively.
3.3. Hirshfeld surfaces analyses
In recent years, molecular crystal structure analysis using tools
based on Hirshfeld surface has rapidly gained in popularity [20]. As
a method for obtaining crystal stacking trend information, the
derivation of the Hirshfeld surface and the decomposition of 2D
fingerprints provide an intuitive and convenient method for quan-
titative analysis of the interactions in the crystal structure [21a].
The study of stacked patterns reveals the similarities and differ-
ences between related structures, provides great potential for the
development of crystal engineering, and provides insight into the
nature and strength of interactions between molecular crystal
components [22]. We use CrystalExplorer to produce Hirshfeld sur-
face and map parameters on them to analyze the intermolecular
interactions [23].
Fig. 6. View of the one-dimensional supramolecular structure of complex 2. C9-
The interactions between molecules were analyzed using the
dnorm mapping on the Hirshfeld surface (Fig. 12a). The molecular
surface showed a large dark red, indicating the existence of hydro-
gen bonds interactions [21b], at the same time, the interacting
H9ABÁÁÁCg2#9 interactions of complex 2 (Cg 2 is the centroids of atoms C11/C12/
#9
C13/C14/C15/C16.), symmetry code:
= 1-x, 2-y, 1-z. The disordered positions O
atoms of O5 only show the more populated position and the hydrogen atoms and
solvent molecules are omitted for clarity.
Fig. 7. The three-dimensional supramolecular structure of complex 2 is formed by intermolecular hydrogen bonds O8-H8ÁÁÁO11#1, O11#4-H11#4ÁÁÁO7, C9-H9AAÁÁÁO3#5, C15-
H15ÁÁÁO11#4 and C22#6-H22B#6ÁÁÁO2. Symmetry code: #1 = 1-x, 1-y, 1-z; #4 = -x, 2-y, 1-z; #5 = 1-x, 1-y, 2-z; #6 = x, 1 + y, z. The disordered positions O atoms of O5 only show the
more populated position and the hydrogen atoms are omitted for clarity.
7

P. Li, Shi-Zhen Li, Yu-Xin Wei et al.
Polyhedron 204 (2021) 115267
Fig. 10. The two-dimensional supramolecular structure of complex 3 is formed by
C21-H21BÁÁÁ Cg1#5, C21-H21AÁÁÁCg2 and Cg2#10ÁÁÁCg2#1 and interactions, symmetry
#1
#5
#10
code:
= 1-x, 1-y, 1-z;
= 1-x, 1-y, 2-z;
= -x, 1-y, 1-z. Hydrogen atoms are
Fig. 9. The two-dimensional supramolecular structure of complex 3 is formed by
omitted for clarity.
intermolecular hydrogen bonds O8-H8ÁÁÁO11, O11-H11ÁÁÁO10#1
, -
C9#10-H9B#10
#1
#5
ÁÁÁO7#1 and C20-H20CÁÁÁO11#5, symmetry code:
= 1-x, 1-y, 1-z;
= 1-x, 1-y, 2-
#10
z;
= -x, 1-y, 1-z. Hydrogen atoms are omitted for clarity.
an index of
pÁÁÁp stacking interaction [19b]. The ratio of inter-
molecular interactions that stabilize the crystal structure can be
determined by analyzing the 2D fingerprint plot (Fig. 13) [24].
For complex 1, HÁÁÁH, OÁÁÁH/HÁÁÁO, CÁÁÁH/HÁÁÁC, CÁÁÁO and CÁÁÁC interac-
tions are 42.4, 34.6, 14.2, 2.9 and 0.0%, respectively. For complex 2,
HÁÁÁH, OÁÁÁH/HÁÁÁO, CÁÁÁH/HÁÁÁC, CÁÁÁO and CÁÁÁC interactions are 53.6,
29.5, 10.5, 2.5 and 0.7%, respectively. For complex 3, HÁÁÁH, OÁÁÁH/
HÁÁÁO, CÁÁÁH/HÁÁÁC, CÁÁÁO and CÁÁÁC interactions are 47.6, 36.1, 10.6,
0.3 and 2.1%, respectively. Through quantitatively determined of
atoms from the neighboring molecules have been shown and
marked in detail in Fig. 11, which corresponds to the supramolec-
ular structures of the complexes 1–3. The small area and light color
on the dnorm indicated weak and longer interactions, rather than
hydrogen bonds. Shape index is a qualitative measure of surface
shape, red zones complement blue zones can be observed on the
shape index of complexes 1–3, which provided the expected equal
triangles for the interactions between the aromatic rings (Fig. 12b)
[19b], at the same time, there are large flat areas on curvedness of
the intermolecular interactions, we can find that the
pÁÁÁp stacking
interactions in complexes 1–3 have obvious difference (3 > 2 > 1),
there are consistent with the supramolecular structures of com-
plex 1–3. From the 2D fingerprint plot, we can find that HÁÁÁH
complexes 1–3 (Fig. 12c), they indicated the
pÁÁÁ
p stacking
interactions in complex 1–3, we can include CÁÁÁ C interaction as
Fig. 11. dnorm surfaces of complexes 1–3, the interacting atoms from the neighboring molecules have been shown and marked in detail, highlighting the hydrogen bonding
motifs.
8

P. Li, Shi-Zhen Li, Yu-Xin Wei et al.
Polyhedron 204 (2021) 115267
tures, intermolecular interactions play key roles in the stacking
mode of complexes 1–3.
3.4. Fluorescence properties
The design and synthesis of optical (colorimetric and fluores-
cent) molecular probes have aroused great interest in a variety of
scientific communities. In order to develop the related applica-
tions, salamo-based ligands and their complexes have been widely
reported as chemical sensors [14a,15a,15b].
Fluorescence property experiments were performed in EtOH
solution with the concentration of the ligand is 1 Â 10-5 mol/L, at
the same time, excitation wavelength is 280 nm, the titration
curves of complexes 1–3 are depicted in Fig. 14. The strong emis-
sion band of the ligand was observed at about 325 nm, which is
attributed to the
[10a]. For complexes 1 and 2, with the gradual addition of Co2+
(1
10-3 mol/L), the fluorescence intensity of the ligand
decreased gradually, and the decreasing trend of the fluorescence
intensity stopped when Co2+ ions were added to 1.5 equivalents
(Fig. 14a) [9c,12c], The ligand H2L as the signaling unit, when the
metal atoms self-assemble with it, causing the excited state
p-p* charge transition of the ligand molecules
Fig. 12. Hirshfeld surfaces analyses mapped with (a) dnorm, (b) Shape index, (c)
Curvedness of complexes 1–3.
Â
and OÁÁÁH/HÁÁÁO are the main interactions between the molecules of
the complexes, which is mainly the effect of the oxygen atoms of
the nitro groups, there is also confirmed in supramolecular struc-
Fig. 13. The fingerprint plots for complexes 1–3 and the relative contributions of all contacts.
Fig. 14. (a) Fluorescence spectra of H2L (1 Â 10-5 M) with addition of various concentrations of Co2+ (1 Â 10-3 M). (b) Fluorescence spectra of H2L (1 Â 10-5 M) with addition of
various concentrations of Ni2+ (1 Â 10-3 M).
9

P. Li, Shi-Zhen Li, Yu-Xin Wei et al.
Polyhedron 204 (2021) 115267
(b) C.B. Provis-Evans, S. Lau, V. Krewald, R. Webster, ACS Catal. 10 (2020)
10157;
electrons of the ligand transfer to the empty orbitals of the metal
atoms (LMCT), which shows strong fluorescence quenching
[13b,13d]. At the same time, the fluorescence of the Co2+
complexes have a red-shift of 7 nm relative to the ligand. The
fluorescence titration curves of complex 3 are the same as that of
the former two, the fluorescence of the Ni2+ complexes have a
red-shift of 8 nm relative to the ligand (Fig. 14b).
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4. Conclusion
Through wet-chemical method, three trinuclear complexes 1–3
were successfully synthesized, which belongs to (L)3-: M(II) = 2:3
type homo-polynuclear complexes with inversion centers. The
interactions of the complexes were quantitatively analyzed by Hir-
shfeld surface and 2D fingerprints, HÁÁÁH and OÁÁÁH/HÁÁÁO are the
main interactions between the molecules of the complexes, at
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the same time, p-p stacking interactions of complexes 1–3 are sig-
nificantly different (3 > 2 > 1), meantime, the oxygen atoms of the
nitro groups play important roles in the formation of intermolecu-
lar hydrogen bonds, which is consistent with the supramolecular
structures of complexes 1–3. The ligand H2L has strong emission
band at about 325 nm, but the complexes show strong fluores-
cence quenching and red-shift relative to the ligand.
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Declaration of Competing Interest
(b) J.F. Wang, R.N. Bian, T. Feng, K.F. Xie, L. Wang, Y.J. Ding, Microchem. J. 160
(2021) 105676;
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared
to influence the work reported in this paper.
(c) C. Liu, Z.L. Wei, H.R. Mu, W.K. Dong, Y.J. Ding, J. Photochem. Photobio. A 397
(2020) 112569.
[10] (a) P. Li, G.X. Yao, M. Li, W.K. Dong, Polyhedron 195 (2021) 114981;
(b) R.N. Bian, J.F. Wang, X. Xu, X.Y. Dong, Y.J. Ding, Appl. Organomet. Chem. 35
(2021) e6040;
(c) M. Yu, Y. Zhang, Y.Q. Pan, L. Wang, Inorg. Chim. Acta 509 (2020) 119701.
[11] C. Liu, X.X. An, Y.F. Cui, K.F. Xie, W.K. Dong, Appl. Organomet. Chem. 34 (2020)
e5272.
Acknowledgement
[12] (a) Y.F. Cui, C. Liu, Y. Zhang, Y. Zhang, Inorg. Nano-Met. Chem. 51 (2021) 288;
(b) X.X. An, Z.Z. Chen, H.R. Mu, L. Zhao, Inorg. Chim. Acta 511 (2020) 119823;
(c) Y. Zhang, M. Yu, Y.Q. Pan, Y. Zhang, L. Xu, X.Y. Dong, Appl. Organomet.
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This work was supported by the National Natural Science Foun-
dation of China (21761018), which is gratefully acknowledged.
(d) Y. Zhang, Y.J. Li, S.Z. Guo, T. Fu, L. Zhao, Transit. Met. Chem. 45 (2020) 485.
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