Seven Zn(II) and Cd(II) 1D coordination polymers based on azine donor linkers and decorated with 2-thiophenecarboxylate: Syntheses, structural parallels, Hirshfeld surface analysis, and spectroscopic and inclusion properties

Article abstract of DOI:10.1016/j.poly.2020.114702

Seven mixed-ligand 1D coordination polymers [Zn₂(4-bphz)(2-tpc)₄]_n (1), [Zn₂(4-bpmhz)(2-tpc)₄]_n (2), [Cd(4-bphz)₂(2-tpc)₂]_n (3), [Zn(3-bphz)(2-tpc)₂

Full text of DOI:10.1016/j.poly.2020.114702

Journal Pre-proofs
Seven Zn(II) and Cd(II) 1D coordination polymers based on azine donor link‐
ers and decorated with 2-thiophenecarboxylate: syntheses, structural parallels,
Hirshfeld surface analysis, and spectroscopic and inclusion properties
Vasile Lozovan, Victor Ch. Kravtsov, Eduard B. Coropceanu, Nikita Siminel,
Olga V. Kulikova, Natalia V. Costriucova, Marina S. Fonari
PII:
S0277-5387(20)30359-4
DOI:
Reference:
https://doi.org/10.1016/j.poly.2020.114702
POLY 114702
To appear in:
Polyhedron
Received Date:
Revised Date:
Accepted Date:
10 June 2020
4 July 2020
6 July 2020
Please cite this article as: V. Lozovan, V. Ch. Kravtsov, E.B. Coropceanu, N. Siminel, O.V. Kulikova, N.V.
Costriucova, M.S. Fonari, Seven Zn(II) and Cd(II) 1D coordination polymers based on azine donor linkers and
decorated with 2-thiophenecarboxylate: syntheses, structural parallels, Hirshfeld surface analysis, and
spectroscopic and inclusion properties, Polyhedron (2020), doi: https://doi.org/10.1016/j.poly.2020.114702
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Seven Zn(II) and Cd(II) 1D coordination polymers based on azine donor linkers and decorated
with 2-thiophenecarboxylate: syntheses, structural parallels, Hirshfeld surface analysis, and
spectroscopic and inclusion properties
Vasile Lozovan 1,2, Victor Ch. Kravtsov 3, Eduard B. Coropceanu 1,2, Nikita Siminel 3,
Olga V. Kulikova 3, Natalia V. Costriucova 3, Marina S. Fonari 3,*
1
Institute of Chemistry, 3 Academiei str.,Chisinau, Republic of Moldova;
E-mails: lozovanvasile90@gmail.com; coropceanu.eduard@ust.md;
2
Tiraspol State University, 5 Iablocikin str., Chisinau, Republic of Moldova;
3
Institute of Applied Physics, 5 Academiei str., Chisinau, Republic of Moldova;
E-mails: kravtsov@phys.asm.md; siminel.n@gmail.com; olga.kulikova@phys.asm.md;
constriucova@phys.asm.md; fonari.xray@phys.asm.md
* Correspondence: fonari.xray@phys.asm.md; fonari.xray@gmail.com
A B S T R A C T: Seven mixed-ligand 1D coordination polymers [Zn2(4-bphz)(2-tpc)4]n (1),
[Zn2(4-bpmhz)(2-tpc)4]n (2), [Cd(4-bphz)2(2-tpc)2]n (3), [Zn(3-bphz)(2-tpc)2]n (4), [Zn(3-bpmhz)(2-tpc)2]n (5),
[Cd(4-bpmhz)(2-tpc)2]n·0.5n(4-bpmhz) (6), [Cd(3-bpmhz)(2-tpc)2]n· 0.5n(H2O) (7) (where 2-tpc =
2-thiophenecarboxylate,
4-bphz
=
1,2-bis(pyridin-4-ylmethylene)
hydrazine,
4-bpmhz
=
1,2-bis(1-(pyridin-4-yl)ethylidene)hydrazine, 3-bphz = 1,2-bis(pyridin- 3-ylmethylene)hydrazine, and
3-bpmhz = 1,2-bis(1-(pyridin-3-yl)ethylidene)hydrazine) were prepared and studied using spectroscopic
(FTIR, UV-Vis) and X-ray diffraction methods of analysis. Similarly, four bidentate-bridging azine ligands
provide the polymers’ extension, while the different mononuclear/binuclear metal nodes demonstrate the
variable metals’ coordination capacities that influence the crystal packing motifs and inclusion properties. The
guest-free arrays 1–5 pack in parallel stacking modes, while the inclusion compounds 6 and 7 reveal
criss-cross packing arrangements with large channels where guest molecules (4-bpmhz/water) serve as
structure-directing templates in the formation of crystal structures. The distributions of different types of
intermolecular interactions with respect to the percentage of stacking interactions in 1–7 were quantified by
Hirshfeld surface and fingerprint plots analysis. The guest-exchange properties for 6 and the solid state
emissive properties for 1–7 are reported.
Keywords: azomethyne ligands; coordination polymers; crystal structure; spectroscopic studies; inclusion
properties; luminescence
1. Introduction
Coordination polymers as an emerging type of multifunctional material is a growing field that has inspired
scientists worldwide already for more than two decades [1]. The numerous studies report rigid
three-dimensional coordination frameworks (MOFs) as sponge materials with desired pore volumes and
1

selectivity in adsorption [2, 3]. Otherwise, lower-dimensional (one- and two-dimensional) coordination arrays
whose crystal structures along with coordination bonds are sustained predominantly by noncovalent
interactions weaker than coordination bonds, such as halogen or hydrogen bonding, - stacking etc. beside
their magnetic, electrical, mechanical, optical properties, also show potential as soft adsorption materials, being
responsive to guest adsorption/desorption events through the gate-opening mechanism originating from their
structural flexibility. They reveal fascinating properties such as so-called breathing and swelling phenomena as
a function of host–guest interactions [4-11]. The single-crystal-to-single-crystal transformations that often
accompany the adsorption–desorption events and occur in a reversible/irreversible manner can be registered by
X-ray diffraction facilities as well as by optical response [12-15].
The mixed-ligand synthetic approach that manipulates by at least two different ligands (acid/acid;
acid/base; base/base) shows high efficacy for tuning the structures and spectrum of properties of final
coordination compounds [16-18]. The rational choice of co-ligands is especially challenging when aiming to
combine antagonistic properties, for example, adsorption, where big pores and low crystal densities are
demanded, and luminescence, which, contrarily, needs a high density and favorable arrangement of the
luminophore, to register the ligand-based response [19]. Schiff-base ligands with a spectrum of useful
properties [20] are widely used as linkers in coordination polymers [21]. Recently, we demonstrated the
function of some Schiff-base luminophores as bidentate mediators in hybrid inorganic–organic Zn(II) and
Cd(II) neutral coordination networks with luminescent properties where inorganic anions (nitrate, iodide,
sulfate) act as co-ligands and complete the metals’ coordination cores [22-24]. Herein, we intend to replace the
inorganic anion from the starting Zn(II) and Cd(II) nitrate salts with a carboxylate anion, namely,
2-thiophenecarboxylate. The choice of 2-thiophenecarboxylic acid as a useful co-ligand originates from two
main points. On the one hand, the survey of CSD (CSD version 5.40, updates Feb 2019) for this ligand reveals
a diversity of coordination modes that give access to structural variety in the forms of Zn(II) and Cd(II)
mononuclear compounds [25-27], heterometallic Zn(II)-Eu(III)/Tb(III) [28, 29], complexes, and coordination
mixed-ligand polymers such as the Ag(I) double chain with 3-aminopyridine [30], Cu(II) compounds with
-
2-amino-4,6-dimethoxypyrimidine [31] or azido anion N3 [32], as well as the homoleptic
Zn-2-thiophenecarboxylate coordination polymer [33]. On the other hand, compounds containing
2-thiophenecarboxylic acid demonstrate impressive luminescence properties [28, 34-36], always being the
focus of our research [12, 22-24].
This background motivated us to synthesize a series of seven one-dimensional (1D) coordination polymers
(1–7) based on 2-thiophenecarboxylic acid H(2-tpc) and azine ligands of the bis-monodentate N,N'-donor type,
1,2-bis(pyridin-4-ylmethylene)hydrazine (4-bphz), 1,2-bis(pyridin-3-ylmethylene)hydrazine (3-bphz),
1,2-bis(1-(pyridin-4-yl)ethylidene)hydrazine (4-bpmhz), and 1,2-bis(1-(pyridin-3-yl)ethylidene) hydrazine
(3-bpmhz). The synthetic protocols, crystal structures, and optical properties are reported.
2. Experimental
2.1. Materials and Measurements
Zinc and cadmium nitrates, 4-pyridinecarboxaldehyde, 3-pyridinecarboxaldehyde, 4-acetylpyridine,
3-acetylpyridine, hydrazine sulfate, 2-thiophenecarboxylic acid, and solvents were obtained from commercial
sources (Sigma-Aldrich) and were used without further purification. The IR(ATR) spectra were recorded on a
FTIR Spectrum-100 Perkin Elmer spectrometer in the range of 650–4000 cm−1. Elemental analysis was
performed on a vario EL III Element Analyzer. NMR spectra were recorded on a Bruker spectrometer at
1
400.13 MHz for H and 100.61 MHz for 13C in DMSO-d6. Chemical shifts (δ) are reported in parts per
million (ppm) and are referenced to the residual non-deuterated solvent peak (2.50 ppm for 1H and 39.50 ppm
for 13C). UV–Vis measurements were carried out with a T60 UV/Vis spectrophotometer. Solid state emission
spectra were recorded using a pulse nitrogen laser (λexc=337.1 nm) at 300 K. The excitation pulse duration
was 15 ns, the repetition frequency was 50 Hz, and the pulse energy was 0.2 mJ. The emission was detected
with a FEU-79 instrument (multialkaline photocathode Sb(Na2K) with the adsorbed cesium layer on the
surface, characteristic of the S20 type). The intrinsic time of the detecting system was 20 ns. The afterglow
2

duration (at 300 K) for all the studied compounds was shorter than the time resolution of the detecting
system. Gas adsorption parameters were obtained from N2 adsorption isotherms at 77 K. The adsorption
isotherm was measured using Autosorb-1-MP (Quantachrome). The specific surface area (SBET) was
calculated using the Brunauer−Emmett−Teller (BET) equation. The total pore volume (Vt) was calculated by
converting the amount of N2 gas adsorbed at a relative pressure of 0.99 to equivalent liquid volume of the
adsorbate (N2). The concentration of the metal cations was determined using an atomic absorption
spectrophotometer, Shimadzu AA-7000. The guest evacuation from compound 6 was performed in the
glycerine bath under a vacuum created by the water jet vacuum pump, maintaining a constant temperature.
X-ray powder diffraction data were collected with a DRON-UMB X-ray powder diffractometer equipped
with a Fe−Kα radiation (λ = 1.93604 Å) source. The diffractometer was operated at 30 kV and 30 mA. The
data were collected over an angle range of 5°−50° at a scanning speed of 5° per minute.
2.2. Synthesis of the Schiff-Base Ligands
In the reported source [41], the hydrazine hydrate was used in the synthesis of these ligands. We used the
hydrazine sulfate salt by adding sodium carbonate to bring the solution to a neutral pH. The synthetic
protocols and spectral details are given in [23, 24]. Na(2-tpc) was obtained by neutralizing H(2-tpc) with
NaOH in water, using equimolar amounts of reagents. The water was then removed by means of a rotary
evaporator.
2.3. Synthesis of [Zn2(4-bphz)(2-tpc)4]n (1)
In a beaker, 0.06 g (0.2 mmol) of Zn(NO3)2·6H2O and 0.06 g (0.4 mmol) of Na(2-tpc) were dissolved in 8
mL of H2O. In another beaker, 0.042 g (0.2 mmol) of 4-bphz was dissolved in 8 mL of EtOH. The 4-bphz
ligand solution was added, without stirring, to the solution of the first beaker. The beaker was covered with
parafilm. After 3 days, yellow crystals formed. Yield: ~ 60%. Anal. calc. for C16H11N2O4S2Zn (%): C, 45.24;
H, 2.61; N, 6.59; O, 15.07; S, 15.10. Found (%): C, 44.92; H, 2.41; N, 6.34; O 14.87; S, 14.89. IR-ATR
(cm-1): 3090 w, 3067 w, 1625 s, 1616 s, 1525 m, 1423 vs, 1388 vs, 1347 m, 1312 m, 1224 m, 1208 w, 1119 w,
1064 w, 1032 m, 976 w, 954 w, 859 w, 829 m, 799 m, 766 vs, 708 vs, 694 s, 656 s.
2.4. Synthesis of [Zn2(4-bpmhz)(2-tpc)4]n (2)
The compound was obtained under the same conditions as 1, except Zn(NO3)2·6H2O and Na(2-tpc) were
dissolved in a mixture of 4 mL of H2O and 6 mL of MeOH and the ligand 4-bpmhz was dissolved in 10 mL of
MeOH. The glass was covered with parafilm. After 1 day, yellow-orange crystals formed. Yield: ~ 55%.
Anal. Calc. for C17H13N2O4S2Zn (%): C, 46.53; H, 2.99; N, 6.38; O, 14.58; S, 14.61. Found (%): C, 46.23;
H, 2.75; N, 6.29; O, 14.32; S, 14.50. IR-ATR (cm-1): 3088 w, 3069 w, 2925 w, 1625 s, 1614 s, 1523 m, 1421
vs, 1384 vs, 1346 s, 1288 m, 1222 m, 1115 m, 1078 w, 1064 m, 1031 m, 974 w, 854 w, 835 m, 798 m, 769 vs,
722 s, 712 vs, 665 s.
2.5. Synthesis of [Cd(4-bphz)2(2-tpc)2]n (3)
The compound was obtained under the same conditions as 1. After 1 day, yellow crystals formed. Yield:
~ 52%. Anal. Calc. for C34H26CdN8O4S2 (%): C, 51.88; H, 3.33; N, 14.24; O, 8.13; S, 8.15. Found (%): C,
51.65; H, 3.10; N, 14.03; O, 7.99; S, 8.01. IR-ATR (cm-1): 3070 w, 3051 w, 2987 w, 1606 m, 1548 s, 1519 s,
1422 vs, 1382 vs, 1338 s, 1310 m, 1225 m, 1120 m, 1065 m, 1041 w, 1029 w, 1014 m, 976 w, 952 m, 904 w,
888 w, 864 m, 856 m, 819 m, 806 s, 774 s, 717 w, 696 m, 686 m.
2.6. Synthesis of [Zn(3-bphz)(2-tpc)2]n (4)
A solution of 0.03 g (0.1 mmol) of Zn(NO3)2·6H2O and 0.03 g (0.2 mmol) of Na(2-tpc) in 3 mL of H2O
was added to a test tube. Thereafter, a solution of 0.026 g (0.12 mmol) of 3-bphz dissolved in 3 mL of EtOH
was added carefully. The tube was covered with parafilm. After 3 days, in the middle of the tube, yellow
3

crystals formed. Yield: ~ 80%. Anal. Calc. for C22H16N4O4S2Zn (%): C, 49.86; H, 3.04; N, 10.57; O, 12.08;
S, 12.10. Found (%): C, 49.57; H, 2.95; N, 10.31; O, 11.89; S, 11.94. IR-ATR (cm-1): 3090 w, 3076 w, 3052
w, 2925 w, 1639 m, 1606 vs, 1582 m, 1516 m, 1486 w, 1419 vs, 1360 vs, 1334 vs, 1315 vs, 1236 m, 1218 m,
1192 m, 1121 m, 1107 m, 1060 m, 1027 m, 970 m, 877 m, 858 m, 799 s, 775 vs, 748 s, 717 vs, 690 vs, 655 s.
2.7. Synthesis of [Zn(3-bpmhz)(2-tpc)2]n (5)
In a beaker, 0.06 g (0.2 mmol) of Zn(NO3)2·6H2O and 0.06 g (0.4 mmol) of Na(2-tpc) were dissolved in 4
mL of H2O. In another beaker, 0.055 g (0.23 mmol) of 3-bpmhz was dissolved in 5 mL of MeOH. The 3-bpmhz
ligand solution was added to the solution of the first beaker. Initially, a yellow-orange sediment was formed,
which dissolved when the mixture was stirred. The solution was filtered off into another beaker and covered
with parafilm. After 1 day, yellow-orange crystals formed. Yield: ~ 55%. Anal. Calc. for C24H20N4O4S2Zn
(%): C, 51.66; H, 3.61; N, 10.04; O, 11.47; S, 11.49. Found (%): C, 51.48; H, 3.25; N, 9.86; O, 11.24; S,
11.27. IR-ATR (cm-1): 3101 w, 3072 w, 2922 w, 1587 vs, 1524 s, 1482 m, 1423 vs, 1396 vs, 1365 vs, 1340 s,
1296 m, 1224 m, 1192 m, 1127 m, 1112 m, 1077 m, 1031 m, 967 w, 933 w, 860 m, 818 s, 795 s, 772 vs, 710 vs,
696 vs, 654 s.
2.8. Synthesis of [Cd(4-bpmhz)(2-tpc)2]n·0.5n(4-bpmhz) (6)
In a beaker, 0.06 g (0.2 mmol) of Cd(NO3)2·4H2O and 0.06 g (0.4 mmol) of Na(2-tpc) were dissolved in
10 mL of H2O. In another glass, 0.071 g (0.3 mmol) of 4-bpmhz was dissolved in 10 mL of EtOH. The
4-bpmhz ligand solution was added without stirring to the solution of the first beaker. The beaker was
covered with parafilm. After 1 hour, yellow-orange crystals formed. Yield: ~ 90%. Anal. Calc. for
C31H27CdN6O4S2 (%): C, 51.42; H, 3.76; N, 11.61; O, 8.84; S, 8.86. Found (%): C, 51.24; H, 3.49; N, 11.41;
O, 8.65; S, 8.67. IR-ATR (cm-1): 3077 w, 2966 w, 2922 w, 1604 m, 1547 s, 1518 s, 1420 vs, 1384 vs, 1368 s,
1343 s, 1290 m, 1238 w, 1218 m, 1114 w, 1061 m, 1044 m, 1028 m, 1014 m, 975 w, 879 w, 860 w, 830 s, 809
s, 774 vs, 759 s, 725 s, 710 vs, 653 s.
2.9. Synthesis of [Cd(3-bpmhz)(2-tpc)2]n·0.5n(H2O) (7)
In a beaker, 0.06 g (0.2 mmol) of Cd(NO3)2·4H2O and 0.06 g (0.4 mmol) of Na(2-tpc) were dissolved in
10 mL of H2O. In another beaker, 0.048 g (0.2 mmol) of 3-bpmhz was dissolved in 10 mL of MeOH. The
3-bpmhz ligand solution was added without stirring to the solution of the first beaker. The beaker was
covered with parafilm. After 1 hour, yellow-orange crystals formed. Yield: ~ 85%. Anal. Calc. for
C48H40Cd2N8O8S4 (%): C, 47.65; H, 3.33; N, 9.26; O, 10.58; S, 10.60. Found (%): C, 47.48; H, 3.24; N,
9.05; O, 10.38; S, 10.43. IR-ATR (cm-1): 3477 w, 3069 w, 2921 w, 1613 m, 1601 m, 1547 s, 1521 s, 1475 m,
1423 vs, 1386 vs, 1369 vs, 1342 s, 1293 m, 1225 m, 1196 m, 1119 m, 1086 w, 1044 m, 1029 s, 969 w, 938 w,
859 m, 813 s, 775 vs, 754 s, 743 s, 722 s, 693 vs.
2.10. Crystal structures of 1–7
Single crystal X-ray diffraction measurements for 1–7 were carried out on an Xcalibur E diffractometer
equipped with a CCD area detector and a graphite monochromator utilizing MoKα radiation at room
temperature. Final unit cell dimensions were obtained and refined on an entire data set. All the calculations to
solve the structures and to refine the models proposed were carried out with the programs SHELXS97 and
SHELXL2014 [37, 38]. Hydrogen atoms attached to carbon atoms were positioned geometrically and treated as
riding atoms using SHELXL default parameters with Uiso(H)=1.2Ueq(C) and Uiso(H)=1.5Ueq(CH3). Compound
7 was refined as a non-merohedral two-component twin. In 1–4, 6, and 7, the thiophene ring portion of
coordinated 2-tpc ligands were disordered over two orientations relative to one another by a 180° rotation and
were refined, constraining their respective occupancies to add up to one. The X–ray data and the details of the
refinement for 1–7 are summarized in Table 1, and selected geometric parameters are given in Table S1. The
Figures were produced using Mercury [39]. The solvent accessible areas were evaluated using Mercury [39]
and PLATON [40] facilities.
4

3. Results
3.1. Generals
The reported 1D coordination polymers 1–7 (Scheme 1) were obtained by a diffusion method and slow
evaporation solution technique without stirring and heating, either in the glass beaker or in the test tube,
starting from Zn(II) or Cd(II) nitrate salts, sodium 2-thiophenecarboxylate, and four azomethine ligands. The
crystal images for 1–7 are shown in Fig. 1. Crystal colors vary from yellow to orange-red.
O
CH3
N
CH3
N
N
N
N
N
N
N
N
N
N
ONa
N
N
N
N
N
S
H3C
H3C
(4-bphz)
4-bpmhz
Na(2-tpc)
(3-bphz)
3-bpmhz
H2O/EtOH
H2O/EtOH
H2O/EtOH
Zn(NO3)2 + 4-bphz + 2Na(2-tpc)
Zn(NO3)2 + 4-bpmhz + 2Na(2-tpc)
[Zn2(4-bphz)(2-tpc)4]n
(1)
[Zn2(4-bpmhz)(2-tpc)4]n
[Cd(4-bphz)2(2-tpc)2]n
(2)
(3)
Cd(NO3)2 + 4-bphz + 2Na(2-tpc)
Zn(NO3)2 + 3-bphz + 2Na(2-tpc)
Zn(NO3)2 + 3-bpmhz + 2Na(2-tpc)
Cd(NO3)2 + 4-bpmhz + 2Na(2-tpc)
Cd(NO3)2 + 3-bpmhz + 2Na(2-tpc)
H2O/EtOH
H2O/EtOH
[Zn(3-bphz)(2-tpc)2]n
[Zn(3-bpmhz)(2-tpc)2]n
(4)
(5)
H2O/EtOH
H2O/EtOH
[Cd(4-bpmhz)(2-tpc)2]n
n(4-bpmhz) (6)

[Cd(3-bpmhz)(2-tpc) ] 0.5n(H O)
(7)
2 n
2
Scheme 1. Schematic pathway for coordination polymers 1–7.
(a)
(b)
( c)
( d)
( e)
(f)
(g)
Fig. 1. Crystal images for compounds 1–7 (a-g).
3.2. Crystal structures
Compounds 1–7 crystallize as single and double ladder-type coordination chains. The decisive factors are
the differences in the metals’ atomic radii, positions of binding sites and presence/absence of the methyl
substituents in the azine luminophores. The bond distances and angles in the metals’ coordination polyhedra in
1–7 have common values, and the numerical values are summarized in Table S1. In all these compounds, the
crystal packings are governed predominantly by weak intermolecular forces, which were visualized using the
Hirsfeld surface (HS) analysis protocols and quantified by fingerprint plots [42, 43].
Single chains
Two compounds [Zn2(4-bphz)(2-tpc)4]n (1) and [Zn2(4-bpmhz)(2-tpc)4]n (2), are isostructural (Table 1),
both comprising linear chains and crystallizing in the centrosymmetric triclinic P-1 space group with one Zn(II)
atom, two tpc residues, and a half of the 4-bphz/4-bpmhz chromophore in the asymmetric units. In the linear
5

chains, the binuclear [M2(CO2)4] paddle-wheel building units alternate with bridging 4-bphz/4-bpmhz ligands,
with a metal/chromophore ratio of 1:0.5. The fragments of polymeric chains are shown in Fig. 2a,b. In the
binuclear centrosymmetric [M2(CO2)4] units, Zn(II) atoms take the square-pyramidal NO4 geometries. One of
the 2-tpc residues is situated virtually in the plane of the bridging planar chromophore, while another stands
almost orthogonally to this plane, indicated by the dihedral angles for 2-tpc/4-bphz(4-bpmhz) of 86.2(3) in 1
and 82.8(7) in 2. The Zn…Zn separations across the bridging chromophores are 15.345(2) in 1 and 15.283(1) Å
in 2. In 1, the parallel chains run along the direction [2 0 1] with the interdigitating 2-tpc moieties (Fig. 2c,d). In
1, between the chains, translated along the crystallographic [0 1 1] direction, the stacking patterns include the
heteromeric overlay py(pyridine)···thio(thiophene), as indicated by separation Cg(py)···Cg(thio) = 3.936 Å, a
homomeric overlay with Cg(thio)···Cg(thio) = 3.503 Å and an interplanar separation between the thiophene
rings of 3.385 Å. Fig. S1g visualizes the stacking areas. Despite the interplanar separation between the pyridine
rings being 3.359 Å, the Cg(py)···Cg(py) separation of 4.617 Å indicates a lack of this type of homomeric
stacking. Along the b axis, the chains meet by the 2-tpc residues with a Cg(thio)···Cg(thio) separation of 4.447
Å (4.259 Å in 2), excluding meaningful stacking contributions along the b-axis. In compound 2, where the
N,N’-bridge is decorated by methyl groups, the packing of coordination chains is the same as in 1, with the
further increased distance of Cg(py)···Cg(py) of up to 5.288 Å due to steric hindrances from the methyl groups,
and only heteromeric stacking, py···thio with Cg(py)···Cg(thio) = 3.561 Å, remains meaningful (Fig. S3g).
Similar 1D coordination polymers with the paddle-wheel units, [Cu2(2-tpc)4(omp)]n (where omp =
2-amino-4,6-dimethoxypyrimidine)
[31]
and
[Cu2(2-tpc)4(N-Menia)]n
(where
N-Menia
=
N-methylnicotinamide) [44], were reported.
(a)
(b)
(c)
(d)
Fig. 2. (a) Fragment of a coordination chain in 1. The asymmetric unit is labelled. (b) Fragment of a
coordination chain in 2. The asymmetric unit is labelled. (c) Packing of the chains along the c axis in
1 with indication of short intermolecular contacts. (d) Fragment of crystal packing in 1, showing the
interdigitated packing mode. H-atoms are omitted.
The compound [Cd(4-bphz)2(2-tpc)2]n (3) crystallizes in the monoclinic P21/n space group (Table 1) with
a Cd(II) atom as a single metal node and a metal/chromophore ratio of 1:2. The asymmetric unit comprises one
Cd(II) atom, two 2-tpc residues, and two 4-bphz chromophores. The coordination geometry of the Cd(II) atom
can be described as a N3O4 pentagonal bipyramid. In the basal plane are situated two bidentate-chelate 2-tpc
residues and one monodentate 4-bphz ligand, while two axial positions occupy two bidentate-bridging 4-bphz
6

ligands (Fig. 3a). It should be mentioned that in both four membered chelate rings, one Cd-O bond is shorter
than the other (Table S1). The rms deviation of the five atoms, N(5), O(1), O(2), O(3), and O(4), in the basal
plane is equal to 0.0684 Å. The terminal 4-bphz ligand, in which one pyridine ring remains uncoordinated, has
a twisted shape indicated by the interplanar angle between the pyridine rings of 85.7(1), while the bridging
4-bphz chromophore is virtually planar, indicated by the interplanar angle between the pyridine rings of
5.14(8), and providing a Cd···Cd separation of 16.1527(7) Å along the linear chains expanded along the c-axis.
The Cd(II) coordination in the basal plane comprises the terminal 4-bphz and 2-tpc ligands, which form a
triangle with dimensions of 14.3 x 16.8 x 17.6 Å as measured between the distal atoms of the ligands. Along the
crystallographic b axis, the parallel chains related by inversion are associated in pairs through weak CH…O
contacts - C(12)-H(12)···O(1)(1-x, 1-y, -z) (H···O, C···O 2.50, 3.306(5)Å, CHO 146°), C(15)-H(15)···O(2)( -x,
1-y, -z) (H···O, C···O, 2.59, 3.317(5) Å, CHO 136°), and C(16)-H(16)···O(1)( 1-x, 1-y, -z) (H···O, C···O, 2.57,
3.375(5) Å, CHO 145°) providing alternating Cd···Cd separations of 8.224 and 10.650 Å and a parallel
arrangement of bridging chromophores with alternating Cg(py)···Cg(py) separations of 4.742 and 6.197 Å
along these double tapes, and a Cg(py)···C(thio) of 3.880 Å indicates a heteromeric stacking component (Fig.
S5g). Along the a axis, the coordination chains are linked via weak edge-to-edge side contacts
C(29)-H(29)···O(4)( x-1, y, z) (H···O, C···O 2.51 3.383(6) Å, CHO 157°) forming the double layer restricted
by terminal dangling 4-bphz ligands. These layers pack in the interdigitated mode along the b axis where they
meet by dangling 4-bphz ligands and are held together via ligand–ligand contacts, C(19)-H(19)···N(8)(x+3/2,
1/2-y, z-1/2) (H···N, C···N, 2.56; 3.341(5) Å;  CHN 141°) (Fig. 3b).
.
(a)
(b)
Fig. 3. (a) Fragment of polymeric chain in 3 with partial labeling scheme. Symmetry transformation
for N4’ : x, y, z+1; (b) Fragment of crystal packing. H-atoms are omitted.
The compound [Zn(3-bphz)(2-tpc)2]n (4) crystallizes in the non-centrosymmetric orthorhombic Pca21
space group (Table 1) and comprises zigzag chains with a Zn(II) atom as a node and a metal/chromophore ratio
of 1:1 (Fig. 4a). The Zn(II) atom has an N2O2 tetrahedral coordination geometry that originates from two
terminal monodentate 2-tpc residues and two bidentate bridging 3-bphz ligands. It is the only compound
amongst 1–7 whose 2-tpc residues coordinate in the monodentate modes. The coordination chains run along
the crystallographic a axis in the crystal with a Zn···Zn separation between the consecutive metal atoms in the
chain of 14.0626(8) Å. The chains stack along the crystallographic b axis with a parallel arrangement of the
bridging ligands (Fig. 4b), providing an interplanar separation of 3.345 Å, and the shortest Cg(py)···Cg(py)
separation of 4.508 Å, with the overlapping fragments being the azine-bridge and py ring of the translated
chromophore (Fig. S7g). Additionally, the weak hydrogen bond C(22)-H(22)···O(2)(x, y-1, z) (H···O, C···O
2.53, 3.157(6) Å, CHO 125 ˚) was registered between the translational chains. Along the c axis, the chains
interdigitate and meet by the 2-tpc residues oriented in the T-shape mode (Fig. 4c).
7

(a)
(b)
(c)
Fig. 4. (a) Fragment of polymeric chain in 4 with partial labeling scheme. (b) Stacking of the chains,
view along the c axis. (c) Fragment of crystal packing. View along c axis. H-atoms are omitted.
Ladder-type chains
.
Three compounds [Zn(3-bpmhz)(2-tpc)2]n (5), [Cd(4-bpmhz)(2-tpc)2]n 0.5n(4-bpmhz) (6), and
.
[Cd(3-bpmhz)(2-tpc)2]n 0.5n(H2O) (7) - all with methylated chromophores, comprise similar ladder-type linear
chains with roughly planar binuclear [M2(CO2)4] building units and a metal:/chromophore ratio of 1:1. The
fragments of chains and crystal packings are shown in Fig. 5a–d. Compounds crystallize in the
centrosymmetric space groups, monoclinic P21/c for 5, I2/a for 6, and triclinic P-1 for 7 (Table 1), respectively.
Similarly, the binuclear [M2(CO2)4] building units reside on inversion centers, and the coordination geometry
of each metal atom is a distorted octahedral with the N2O4 sets of donor atoms. Everywhere, one 2-tpc residue
coordinates in the bidentate-chelate mode, another one, in the bidentate-bridging mode, providing
metal…metal separations in the binuclear nodes of 4.1391(6) Å in 5, 3.9287(6) Å in 6, and 3.9428(8) and
3.996(1) Å in two crystallographically unique chains in 7.
The metal···metal separations across the bridging chromophores are 14.4890(9) Å in 5, 15.8858(8) Å in 6,
and 14.643(1) and 14.633(1) Å in 7. Unlike 1 and 2, in 5–7, all four 2-tpc residues in the binuclear metal
building nodes are situated virtually in the same plane forming the parallelogram with linear dimensions of
about 10.13 x 12.89 Å. This platform is roughly orthogonal to the long axes of the double chains to eliminate
unfavorable steric hindrance from the ligands’ methyl-groups.
The crystal packing in 5 differs from that in 6 and 7. The decisive factor is the presence/absence of the
guest molecules in the crystal lattices. In the guest-free compound 5, the parallel chains propagate along the b
axis with the interdigitating 2-tpc moieties in a manner such that four neighboring tapes meet by the thiophene
rings, which form the helical chains along the b axis with alternating Cg(thio2)···Cg(thio1)···Cg(thio2)
separations of 3.807 Å and 4.554 Å, indicating a discrete homomeric stacking pattern (Figs. 5d, S9g). Bulky
coordination platforms preclude the further rapprochement of the parallel-oriented rigid ladders; however, no
guest-accessible voids were found in 5.
In compounds 6 and 7, the coordination chains pack in the criss-cross modes due to the template functions
of the confined guest molecules, identified as the 4-bpmhz chromophore in 6 and water molecules in 7. In 6, the
chains alternatively related by the inversion center and the two-fold axis stack along the crystallographic a axis
forming an infinite stacking of 4-bpmhz luminophores with alternation of two overlapping patterns -
intra-ladder, py···py, with a Cg(py)···Cg(py) of 3.688 Å, and between the ladders, with an azine bridges
overlap, N···N, shortest separation of 3.685 Å (Figs. 5b, S11g). There is also an overlay of the pairs of thiophene
rings related by inversion, separated by 3.405 Å, and a Cg(thio1)···Cg(thio1) of 3.562 Å. The channels along
the crystallographic a axis comprise 1593 Å3 or 25.7% of the unit cell volume being filled by the 4-bpmhz
chromophores. In compound 7, two crystallographically unique chains provide more effective crystal packing
than in 6, with the infinite stacking pattern again, although with the overlapping pyridine rings within and
between the tapes with alternating Cg…Cg separations, 3.690 and 3.760 Å (Figs. S13, S15), the channels fill the
8

dispersed water molecules (Fig. 5f). The voids calculated by PLATON after water removal comprise 631 Å3 or
21% of the unit cell volume.
(a)
(b)
(c)
(d)
(e)
(f)
Fig. 5. (a) Fragment of coordination chain in 5 with partial labeling scheme. Symmetry
transformation for O2’ : -x, -y, 1-z. (b) Fragment of crystal packing in 5. (c) Fragment of coordination
chain in 6 with partial labeling scheme. (d) Fragment of crystal packing in 6. (e) Fragment of one
coordination chain in 7 with partial labeling scheme. Symmetry transformations for O4’ : -x, 2-y, 2-z;
N4’’ : x, y+1, z. (f) Fragment of crystal packing in 7. H-atoms are omitted in crystal packings.
3.3. Hirshfeld surface modeling of coordination polymers 1–7
The size and shape of Hirshfeld surfaces (HS) help to identify intermolecular interactions and classify
molecular crystals in terms of packing similarities [42, 45]. This approach is also useful to highlight subtle
differences among polymorphic forms [46]. Recent studies show the applicability of this method to analyze
9

different types of interactions in coordination polymers, estimating not only the distribution of intermolecular
contacts [47, 48] but also metal–ligand interactions [49]. Having in hand a series of seven coordination
polymers built by the interplay of restricted number of variables (metal and linker), we were curious to
quantify the distribution of intermolecular forces and to determine similarities/dissimilarities using HS
facilities. CrystalExplorer 17 [43] was used to generate the Hirshfeld surfaces [42]. The total dnorm surfaces for
the asymmetric parts of the coordination tapes are shown in Fig. 6, in which the red spots correspond to the
dominant intermolecular interactions in the crystals. The full two-dimensional fingerprints for 1–7 from the
HS analysis [50] are shown in Fig. 7. They clearly indicate different distributions of the interactions for the
asymmetric unit of the coordination polymer in each structure, and even rather subtle differences between
similar systems are highlighted and can be quantified. The main contributions to the total HS areas of the
molecules are depicted by the decomposed dnorm surfaces (Figs. S1, S3, S5, S7, S9, S11, S13, S15) and by the
decomposed fingerprint plots (Figs. S2, S4, S6, S8, S10, S12, S14, S16). The percentages of intermolecular
contributions are summarized in Table 2. The six principal types of interaction are H…H, H···C/C···H,
H···O/O···H, H···N/N···H, S···H/H···S, and C···C contacts, in descending order. The predominant interactions in
all cases are H···H; they appear in the middle of the scattered points in the fingerprint maps, ranging from
38.6% in 5 to 50% in 7. With significantly less contribution, the next most important interactions are
H···C/C···H, that vary from 14.1% in 7 to 24.8 % in 3. The isostructural compounds 1 and 2 reveal the
similarities in the shapes of the fingerprint plots with the predictable wider area for C···H/H···C contacts
originating from the methylated ligand in 2 (Figs. 7a,c, S2, S4). For the family of ladder-type polymers, 5, 6
and 7, the fingerprint plots somewhat differ (Figs. 7d,f–h, S10, S12, S14, S16) demonstrating the symmetrical
distribution of the contacts for the guest-free compound 5 and asymmetry for 6 and 7, imposed by the
different lattice environment. The C···C contacts associated with the - interactions amount to 2.7%-6.7% of
the surface; their presence is indicated by the appearance of red and blue flat areas on the shape-indexed
surfaces (Figs. S1g, S3g, S5g, S7g, S9g, S11g, S13g, S15g).
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
Fig. 6. Hirshfeld surfaces (HS) mapped with dnorm for the complexes 1–6 (a–f) and two unique
fragments in 7 (g,h).
10

(a)
(b)
(c)
(d)
( e)
(f)
(g)
(h)
Fig. 7. Fingerprint plots (full) for compounds 1–6 (a–f) and for two unique fragments in 7 (g, h).
Table 2. Distribution (%) of the principal intermolecular interactions in compounds 1–7.
Compound
H···H
39.5
41.3
C···H/H···C O···H/H···O N···H/H···N S···H/H···S C···C Zn/Cd···all
1
2
20.6
19.3
12.9
12.4
4.7
5.7
2.8
3.5
6.2
5.4
3.0
3.1
3
40.7
24.8
10.2
11.3
1.7
4.3
0.7
4
41.2
23.9
13.0
5.4
4.3
2.7
0.1
5
6
38.6
42.9
15.6
23.1
10.6
11.0
6.3
6.6
9.2
4.1
5.3
6.7
1.2
0.7
7*
Range
40.7/50.0
38.6–50.0 14.1–24.8
17.3/14.1
14.5/9.5
9.5–13.0
3.1/5.5
3.1–11.3
9.6/7.3
1.7–9.6
5.0/6.4
2.7–6.7
2.2/0.7
0.1–3.1
Note: * Values are given for the asymmetric fragments of two coordination tapes defined by Cd1 and
Cd2 atoms in the asymmetric unit.
3.4. IR spectra
The FTIR (ATR) spectra of compounds 1–7 are shown in Figs. S17 and S18. Depending on the
coordination modes, the stretching vibration bands νas and νs of the carboxylate group [51] are registered in
different regions of the spectrum. For two isostructural compounds, 1 and 2, with the same μ2-η1:η1-bridging
coordination mode, two bands νas(COO-) 1616 and νs(COO-) 1388 cm-1 were registered in both. In compounds
6 and 7, with chelating η2 and chelating-bridging μ2- η2: η1 coordination modes, two characteristic bands
νas(COO-) 1547 cm-1 and νs(COO-) ~ 1386 cm-1 were present. In compound 5, chelating η2 and bridging μ2-η1:
η1 modes cause the appearance of three characteristic bands, νas(COO-) 1587 and νs(COO-) 1396 and 1380 cm-1.
For compounds 3 and 4, with the chelating η2 mode, two bands νas(COO-) 1382 and νs(COO-) 1548 cm-1 for 3
and 1360 and 1606 cm-1 for 4 were registered. For Na(2-tpc) salt, three strong characteristic bands at values ca.
1520 and 1420 cm-1 are attributed to the stretching vibration of the 2-thiophene substituted ring [52], and the
band at ca. 1340 cm-1 is attributed to the ν(CSC/thiophene) stretch. These bands are visible in the IR spectra of
the compounds. The deformation band δ(CH) for the aromatic para-substituted, meta-substituted, and
2-thiophenes substituted ring belonging to the corresponding ligands were registered in the range ~850–650
cm-1. The ν(C=N) bands of the imine group with different intensities were identified in the range 1639–1604
11

cm-1. For compounds containing 4-bpmhz and 3-bpmhz ligands, a characteristic strong band in the ~ 1370 cm-1
region was assigned to the symmetrical deformation vibration of the C-H methyl bond δs(CH3). The stretching
vibration bands ν(CH) of weak intensities for carbon atoms Csp3 and Csp2 were found in the range of ~ 3100–
2850 cm-1. Two and three characteristic bands are present for the aromatic ring ν(C=C) of medium and low
intensity ranging from ~ 1600 to 1470 cm-1, which may overlap with the thiophene ring bands. In Figure S18
are marked the indicative ranges for identifying the described functional groups.
3.5. Inclusion and cation-exchange properties of compound 6
Two inclusion compounds, 6 and 7, were tested for their stability to the guest evacuation; however, only 6
withstood the thermal stress while 7 decomposed, so only 6 will be further discussed. To evacuate the guest
molecules from the crystal channels, the compound was heated in vacuo for 6 h at 195 °C; the departure of the
accommodated 4-bpmhz ligand sublimed in the upper part of the walls of the flask (Fig. S19) was confirmed by
the IR spectrum. The mass loss of the guest molecules is in concordance with the theoretical calculations,
16.8% (16.44% calc.) Fig. 8a,b shows the comparative images of the as-synthesised crystals 6 and activated
form 6a, accompanied by the corresponding IR spectra that differ insignificantly (Fig. S20). The N2 sorption
isotherm for the activated product 6a recorded at 77 K (Fig. S21) displays a typical V-type isotherm and
indicates negligible gas uptake, characteristic for systems where the adsorbent–adsorbate interactions are
weak. The calculated BET surface area is 22 m2/g. The pore volume distribution by radius indicates the
presence of mesopores, and the total volume of these pores is also relatively small, 0.113 cm3/g.
In order to study the guest-exchange properties, the activated crystals 6a were immersed in isobutanol
solution for 5 days and in formamide solution for 12 hours. The crystals were then dried at room temperature on
filter paper. The presence of the solvent molecules in the cavities of the compound was identified by recording
IR and NMR spectra (Figs. S20, S22, S23). In the case of isobutanol, broad bands ν(OH) at 3385 cm-1 and
bands ν(CH) at 2952–2871 cm-1 were registered (Fig. 8c). In the case of formamide, the bands ν(C=O) at 1700
cm-1 and νas(NH) and νs(NH) at 3308 and 3169 cm-1 were clearly visible (Fig. 8d). The signals for the guest
molecules were also registered in the 13C and 1H NMR spectra (Figs. S22 and S23).
The reported sources documented the partial or even complete replacements of metal ions constituting
porous frameworks [53-57]. In particular, Cu(II) ions reveal high capacity to substitute metal cations in the
MOF structures, so 6a was tested for cation exchange. For this, 6a was immersed in a 0.2 M aqueous Cu(NO3)2
solution for two weeks. The crystals changed color from yellow-orange to green without a change in the shape
of the crystals during this period (Fig. 8e). The same procedure was undertaken for compound 6, whose
channels were occupied by 4-bpmhz guest molecules, resulting in short (after 5 hours) crystals decomposing in
this solution (Fig. S24) with the formation of green-orange sediment. The relative amounts of the metal cations
Cd(II) and Cu(II) in the doped product 6a–Cu(II) were estimated by the atomic absorption spectroscopy
method (Fig. S25). For the measurement, 50 mg of 6a–Cu(II) were used. According to the calibration graphs
(Fig. S25), 11.62% of copper and 0.21% of cadmium cations were found that resulted in 98.87% of the Cd(II)
cations from product 6a being substituted with Cu(II) cations. The IR spectrum (Fig. 8e) of the 6a–Cu(II)
material indicates that the νas(COO-) band of the 2-tpc anion is shifted to 1602 cm-1 and overlaps with the
ν(C=N) band of the 4-bpmhz ligand (for 6a, this band is at 1554 cm-1), indicating the change in the coordination
mode of the carboxylate group. Additionally, the broad band ν(OH) indicates the presence of water molecules
in this product.
12

(e)
(d)
(c)
OH)
6a-Cu(II)
as(COO-)
s(COO-)
as(NH)
s(NH)
CH)
6a-formamide
C=O)
OH)
6a-isobutanol
6a
(b)
(a)
Compound 6
1600 1400 1200 1000 800
4000
3200
2400
-1
Wavenumber, cm
Fig. 8. IR spectra and images of crystals for compounds: (a) as-synthesized 6; (b) activated product
6a after the elimination of 4-bpmhz guest molecules; (c) 6a–isobutanol product after keeping the
crystals in isobutanol; (d) 6a–formamide product after keeping crystals in formamide; (e) 6a–Cu(II)
product after keeping the crystals in an aqueous solution of Cu(NO3)2.
The comparison of the XRPD patterns for the as-synthesized crystals 6, the thermally activated form 6a,
and the guest-exchange and Cu-doped products (Fig. S26), reveals the retention of crystallinity for all, with
possible phase transition for 6a and 6a–Cu, while for the product 6a–isobutanol, the return to the crystalline
form close to 6 is originated most probably from the compatibility of the molecular volumes of the exchange
guest molecules.
The post-synthetic transformations for 6 were also studied by the UV-Vis spectrophotometric method, and
the absorption curves for 6, 6a, and 6a–Cu(II) were recorded (Fig. 9a). The solutions for analysis were prepared
as already reported [22]. The solutions, with concentrations of 3.3·10-5 M, were prepared taking into account
the elimination of the 4-bpmhz guest molecules for product 6a and the replacement of Cd(II) cations in the
product 6a–Cu(II). The recorded absorption curves have a maximum absorption value at λmax=266 nm, which
confirms the presence of the 4-bpmhz linker in all these compounds. For compound 6, absorption A = 1.53 at
this wavelength. The calculated mass portion of the 4-bpmhz ligand in product 6a according to the molecular
formula is 1/3 lower than in 6. This is also evident from the curve 6a, which has A = 1.08. A close value is also
found in the curve for 6a–Cu(II), A = 1.02, which indicates that the products 6a and 6a–Cu(II) contain a similar
molar fraction of the 4-bpmhz ligand. In the visible domain, the green 6a–Cu(II) sample has a maximum
absorption at 725 nm (Fig. 9b). Fig. 9c depicts the solutions of compounds 6 and 6a–Cu(II) with the same
concentration (0.05 M); the greenish-yellow color is clearly highlighted for the product 6a-Cu(II).
13

C=0.05 M
6a-Cu(II)
1,6
1,4
1,2
1,0
0,8
0,6
0,4
0,2
0,0
C=3.3x10-5
M
6
6a
0,16
0,14
0,12
0,10
0,08
0,06
0,04
6a-Cu(II)
6a-Cu(II)
(0.05 M)
6 (0.05 M)
600
700
800
220 240 260 280 300 320 340
Wavelength (nm)
Wavelength (nm)
(b)
(c)
(a)
Fig. 9. UV-Vis absorption curves: a) compounds 6, 6a, and 6a–Cu(II)—concentration of
solutions, 3.3·10-5 M; b) 6a–Cu(II)—concentration, 0.05 M; c) comparative color images of solutions
6 and 6a–Cu(II)—concentration, 0.05 M.
3.6. Emission properties
The photoluminescence (PL) spectra for the coordination polymers 1–7 and initial azomethine ligands
were registered in the solid state (λexc=337.1 nm) at room temperature. The samples reveal weak emission,
except the 4-bpmhz chromophore, whose strong signal most probably originates from the effective crystal
packing with a significant impact of the stacking component [21] and can be assigned to the -* transition.
The shapes of the emission curves for all samples indicate the superpositions of several radiative processes
(Fig. 10). For the bands’ deconvolution, the Gaussian function was used. The most meaningful peaks were
registered in the long-wavelength region of the spectrum at 1.7, 2.1, 2.3, 2.6, 2.8, and 3.2 eV for all, except
for samples 4 and 5, where the redistribution of the PL intensity is observed in the short-wavelength region of
the spectra. When comparing the PL spectra of the isostructural Zn(II) complexes 1 and 2, it is obvious that
the radiation intensity for 1 based on the 4-bphz chromophore is higher than that for 2 based on the
methylated analog 4-bpmhz in the entire studied region of the spectrum accompanied by the difference in the
curves’ shape. For sample 1, the shape of the emission curve is mainly formed by peaks in the long
wavelength region of the spectrum, 730 nm (1.7 eV), 620 nm (2.0 eV), and 560 nm (2.2 eV). The broad
emission for 5 was registered in the blue region of spectrum, and is formed by peaks at 2.6 eV (475 nm), 2.8
eV (442 nm), and 3.1 eV (400 nm). When comparing the PL spectra of Zn(II) sample 5 and Cd(II) sample 7
based on the same 3-bpmhz ligand, it is obvious that the zinc complex emits more strongly and that the
long-wave peak does not affect the spectrum shape, while for the cadmium complex, the shape of the PL
curve form peaks uniformly located throughout the studied region of the spectrum. The emission quenching
in 6 and 7 is explained by their porous nature.
14

, nm
500
, nm
500
700
600
400
700
600
400
0,40
0,35
0,30
0,25
0,20
0,15
0,10
0,05
1,2
1,0
0,8
0,6
0,4
0,2
0,0
4-bphz
3-bphz
4-bpmhz
3-bpmhz
2
5
6
7
1
3
4
x2
x3
x3
x10
x5
x3
x2
x10
x10
2,0
2,5
3,0
3,5
2,0
2,5
3,0
3,5
h, eV
h, eV
(a)
(b)
Fig. 10. Solid-state emission plots for: (a) nonmethylated 4-bphz, 3-bphz ligands, and compounds 1,
3, and 4 based on these ligands; and (b) methylated 4-bpmhz, 3-bpmhz ligands, and compounds 2 and
5–7 based on these ligands.
4. Conclusions
In conclusion, we report the synthesis of seven 1D Zn(II)/Cd(II) coordination polymers based on the
mixed-ligand strategy. Four azine chromophores were used to provide linear extension, while the 2-tpc ligand
decorated the metal centers, providing access to the mono/binuclear bulky metal building blocks. These
coordination polymers reveal linear and zigzag single and double chains that pack in the parallel mode for
guest-free compounds and reveal criss-cross packing modes when guest molecules are present in the structures.
The easy rearrangement of the rigid coordination arrays is possible due to the weak intermolecular forces,
observed in the crystals from X-ray diffraction data and confirmed by comprehensive Hirshfeld surface
analysis. The criss-cross mode of packing leaves a significant amount of space in the crystal structures
predisposed to the guest exchange as has been demonstrated herein. The reported compounds behave as weak
luminophores.
Appendix A. Supplementary data
CCDC 1997048–1997054 contains the supplementary crystallographic data for 1-7. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or
e-mail: deposit@ccdc.cam.ac.uk.
The following data are available as Supporting Info: Table S1: Bond lengths and angles for 1-7. Figures
S1-S16: Hirshfeld surface images and fingerprint plots for 1-7; Figures S17, S18, S20: IR spectra for
compounds 1-7 and for inclusion compounds of 6; Figure S21: N2 adsorption-desorption isotherms at 77 K for
1
activated compound 6; Figures S22, S23: 13C and H NMR spectra for compound 6 and guest-exchange
products; Figure S25: Calibration curves for Cu(II) and Cd(II) metal cations analyzed by Atomic Absorption
Spectroscopy (AAS); Figure S26: XRPD patterns for compound 6 after modifications.
Acknowledgments: The authors are grateful to Mr. Dr. O. Petuhov for recording the adsorption-desorption
isotherms and Mrs. Dr. T. Mitina for the spectroscopic atomic absorption measurements. V.Ch.K., N.V.C. &
M.S.F. thank the project ANCD 20.80009.5007.15 for support
Conflicts of Interest: The authors declare no conflict of interest.
15

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20

Table 1. Crystal data and structure refinement parameters for 1-7
Compound
1
2
3
4
5
6
7
CCDC number
Empirical formula
1997049
1997051
1997048
1997054
1997052
1997050
1997053
C32H22N4O8 C34H26N4O8S4Z C34H26CdN8O4 C22H16N4O4S2Z C24H20N4O4S2Z C31H27CdN6O4 C48H42Cd2N8O9
S4Zn2
849.51
Triclinic
P-1
n2
S2
787.15
Monoclinic
P21/n
n
n
S2
724.10
Monoclinic
I2/a
S4
Formula weight
Crystal system
Space group
877.57
Triclinic
P-1
529.88
Orthorhombic
557.93
Monoclinic
P21/c
1227.93
Triclinic
P-1
Pca21
Unit cell dimensions
a,Å
b,Å
c,Å
α, °
9.1359(9)
10.2173(9)
11.2253(9)
98.526(7)
108.158
115.093
852.44(15)
1
7.8664(4)
10.6753(6)
12.4681(8)
108.909(5)
97.778(5)
111.412(5)
883.09(10)
1
10.6084(3)
20.3823(5)
16.1527(5)
90
106.643(3)
90
16.2882(7)
6.5813(3)
21.4220(9)
90
8.5567(3)
14.4890(6)
19.4228(10)
90
95.879(3)
90
14.4222(4)
16.8312(5)
26.2099(10)
90
102.903(3)
90
14.6326(9)
14.6431(8)
14.6935(6)
108.053(4)
93.092(4)
94.756(5)
2972.5(3)
2
β , °
90
90
γ, °
Volume, Å3
3346.27(18)
2296.37(16)
2395.33(18)
6201.7(4)
Z
4
4
4
8
3
D(calcd) Mg/m
, mm
F(000)
1.655
1.709
430
1.650
1.653
446
1.562
0.829
1592
1.533
1.288
1080
1.547
1.239
1144
1.551
0.886
2936
1.372
0.909
1236
-1
Reflections collected
4556
5595
11296
5278
8932
10841
21605
Independent reflections
2982 [R(int) 3189 [R(int) = 5909 [R(int) = 3493 [R(int) = 4349 [R(int) = 5627 [R(int) =
21605
= 0.0211]
2437
0.0231]
2744
0.0284]
4632
0.0206]
3066
0.0334]
3178
0.0247]
4241
Reflections with [I>2(I)]
Data / restraints /
parameters
11388
21605 / 32 / 645
2982 / 16 / 3189 / 16 / 286 5909 / 6 / 486
288
3493 / 171 /
385
4349 / 0 / 318
5627 / 6 / 444
2
Goodness-of-fit on F
1.011
0.0349,
0.0717
0.0472,
0.0780
0.290 and
-0.329
1.051
0.0340, 0.0807
1.038
1.035
1.045
1.054
1.029
0.0560, 0.1356
Final R indices [I>2(I)],
R1, wR2
R indices (all data) R1,
wR2
0.0417, 0.0832 0.0319, 0.0705 0.0467, 0.1111 0.0380, 0.0864
0.0427, 0.0867
0.0601, 0.0907 0.0407, 0.0745 0.0730, 0.1242 0.0577, 0.0948
0.1053, 0.1436
Largest diff. peak and hole
0.349 and -0.339
0.748 and
-0.422
0.220 and
-0.293
0.410 and
-0.429
0.431 and -0.555 0.919 and -0.540
-3
e.Å
21

 Mixed-ligand strategy was used for the synthesis of 7 1D coordination polymers;
 Criss-cross crystal packing facilitates guest accommodation
 Solvent-exchange was demonstrated
 The weak intermolecular forces were confirmed by comprehensive Hirshfeld surface
analysis
 Emission properties were registered and discussed
Name
Affiliation
Institute of Chemistry, Chisinau, Moldova;
author (1)
author (2)
Vasile Lozovan
Victor Ch. Kravtsov
Tiraspol State University
Institute of Applied Physics, Chisinau,
Moldova;
Institute of Chemistry; , Chisinau, Moldova;
Tiraspol State University
author (3)
author (4)
author (5)
author (6)
author (7)
Eduard B. Coropceanu
Nikita Siminel
Institute of Applied Physics, Chisinau,
Moldova;
Institute of Applied Physics, Chisinau,
Moldova;
Olga V. Kulikova
Institute of Applied Physics, Chisinau,
Moldova;
Natalia V. Costriucova
Marina S. Fonari
Institute of Applied Physics, Chisinau,
Moldova;
Author’s Contribution
author (1) Investigation , Resources, Visualization , Validation, Writing - original draft
author (2) Investigation, Resources, Methodology, Funding acquisition, Validation, Writing
- review & editing
author (3)
Conceptualization
author (4) Investigation, Visualization
author (5) Investigation, Writing - original draft;
author (6) Formal analysis
author (7) Conceptualization, Visualization, Methodology; Writing - review & editing

Of
seven
mixed-ligand
(2),
1D
coordination
polymers—[Zn2(4-bphz)(2-tpc)4]n
(3), [Zn(3-bphz)(2-tpc)2]n
(1),
(4),
[Zn2(4-bpmhz)(2-tpc)4]n
[Cd(4-bphz)2(2-tpc)2]n
[Zn(3-bpmhz)(2-tpc)2]n (5), [Cd(4-bpmhz)(2-tpc)2]n·0.5n(4-bpmhz) (6), [Cd(3-bpmhz)(2-tpc)2]n·
0.5n(H2O) (7) (where 2-tpc = 2-thiophenecarboxylate, 4-bphz = 1,2-bis(pyridin-4-ylmethylene)
hydrazine, 4-bpmhz = 1,2-bis(1-(pyridin-4-yl)ethylidene)hydrazine, 3-bphz = 1,2-bis(pyridin-
3-ylmethylene)hydrazine, and 3-bpmhz = 1,2-bis(1-(pyridin-3-yl)ethylidene)hydrazine) the
guest-free arrays 1–5 pack in the parallel stacking modes, while the inclusion compounds 6 and 7
reveal criss-cross packing arrangements with large channels where guest molecules
(4-bpmhz/water) serve as structure-directing templates. The distributions of intermolecular
interactions in 1–7 were quantified by Hirshfeld surface and fingerprint plots analysis. The
guest-exchange properties for 6 and the solid state emissive properties for 1–7 are reported.