Synthesis and structure of zinc(II) and cobalt(II) coordination polymers involving the elongated 2′,3′,5′,6′ tetramethylterphenyl-4, 4″-dicarboxylate ligand

Article abstract of DOI:10.1016/j.ica.2020.119500

The elongated linker 2′,3′,5′,6′-tetramethylterphenyl-4,4″-dicarboxylic acid (H₂L) was employed in the synthesis of zinc(II) and cobalt(II) coordination polymers with single or mixed bridging ligands. Seven compounds, that include the solvate H

Full text of DOI:10.1016/j.ica.2020.119500

Journal Pre-proofs
Research paper
Synthesis and Structure of Zinc(II) and Cobalt(II) Coordination Polymers In-
volving the Elongated 2',3',5',6' Tetramethylterphenyl-4, 4''-dicarboxylate Li-
gand
Vasile Lozan, Gamall Makhloufi, Vadim Druta, Paulina Bourosh, Victor Ch.
Kravtsov, Narcisa Marangoci, Christian Heering, Christoph Janiak
PII:
S0020-1693(19)31790-6
https://doi.org/10.1016/j.ica.2020.119500
ICA 119500
DOI:
Reference:
Inorganica Chimica Acta
To appear in:
Received Date:
Revised Date:
Accepted Date:
19 November 2019
3 February 2020
3 February 2020
Please cite this article as: V. Lozan, G. Makhloufi, V. Druta, P. Bourosh, V. Ch. Kravtsov, N. Marangoci, C. Heering,
C. Janiak, Synthesis and Structure of Zinc(II) and Cobalt(II) Coordination Polymers Involving the Elongated 2',3',
5',6' Tetramethylterphenyl-4, 4''-dicarboxylate Ligand, Inorganica Chimica Acta (2020), doi: https://doi.org/
10.1016/j.ica.2020.119500
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover
page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will
undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing
this version to give early visibility of the article. Please note that, during the production process, errors may be
discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2020 Published by Elsevier B.V.

Synthesis and Structure of Zinc(II) and Cobalt(II) Coordination Polymers Involving the
Elongated 2',3',5',6' Tetramethylterphenyl-4, 4''-dicarboxylate Ligand
Vasile Lozan,a,b* Gamall Makhloufic, Vadim Druta,a Paulina Bouroshd, Victor Ch. Kravtsovd, Narcisa
Marangocib, Christian Heeringc, Christoph Janiakc,*
a Institute of Chemistry of MECR, Academiei, str. 3, MD2028, Chisinau, Republic of Moldova
bInstitute of Macromolecular Chemistry ”Petru Poni”, Aleea Gr.Ghica Voda, 41A, Iasi, Romania
cInstitut für Anorganische Chemie und Structurchemie, Heinrich-Heine-Universität Düsseldorf,
Universitätsstr. 1, D-40225 Düsseldorf, Germany
dInstitute of Applied Physics of MECR, Academiei, str. 5, MD2028, Chisinau, Republic of Moldova
Keywords: Zn(II) and Co(II) coordination polymers, linear tetramethylterphenyl
dicarboxylate; mixed ligands.
Abstract: The elongated linker 2',3',5',6'-tetramethylterphenyl-4,4''-dicarboxylic acid
(H2L) was employed in the synthesis of zinc(II) and cobalt(II) coordination polymers with
single or mixed bridging ligands. Seven compounds, that include the solvate H2L·2DMSO
(1·2DMSO), the 1D coordination polymer [Zn(L)(DMF)2]n (2), the two 2D coordination
polymers {[Zn(L)(DEF)]2·2DEF}n (3) and {[Co(L)(DEF)]2·2DEF}n (4), and the three mixed
ligand 3D coordination polymers {[Zn2(L)2(BIBP)]·2DEF}n (5), {[Co2(L)2(BIBP)]·2DEF}n
(6) and {[Zn3(L)3(BIPY)1.5]·4DMF·1.5H2O}n (7), (where DMSO is dimethylsulfoxide, DMF
is dimethylformamide, DEF is diethylformamide, BIBP stands for 4,4′-bis(1-
imidazolyl)biphenyl, and BIPY for 4,4'-bipyridine) have been synthesized and characterized
by IR spectroscopy, thermogravimetry, and single-crystal X-ray diffraction. In 2 the zinc atom
adopts a tetrahedral O4 environment due to the monodentate coordination of two DMF
molecules and two deprotonated bridging L2- ligands. The latter connect the zinc atoms in a
zigzag-like chain. In the coordination polymers 3 to 7 the secondary building unit (SBU) is
the paddle-wheel moiety {M2(O2C-)4(N/O)2}. The metal atoms are five coordinated with
distorted square pyramidal coordination geometry by oxygen atoms from carboxylate groups
of four different L2- linkers, and one axial DEF-O atom in 3 and 4, BIBP-imidazolyl-N atom
in 5 and 6 or BIPY-N atom in 7. Furthermore, the L2- ligands link the SBUs to a (4,4) 2D sql
net. In 5-7 these sql nets are additionally linked by BIBP or BIPY ligands as pillars to provide
pillared-layer 3D and three-fold interpenetrated frameworks. Remarkably, the BIBP pillar
yields bsn (beta-Sn) topology, the BIPY pillar pcu (-Po) topology.
1

1. Introduction
Metal-organic frameworks (MOFs) are constructed from organic ligands and metal ions or
metal clusters [1, 2] and have uniform micropore structures with high surface areas and large
pore volumes. An immense research advancement has been made in the utilization of MOFs
since the past 10-15 years [3, 4], e.g. in catalysis [5–7], gas storage [8–10] and gas separation
[11–13] and recently in cycling heat transformations [14–24]. Numerous overviews or review
articles have been published in the last years indicating the increasing interest in MOF
chemistry [25–29]. In constructing the open frameworks, organic polycarboxylate linkers,
especially rigid linear di- or tri-carboxylic acids, are frequently utilized because they can act
as counter anions and allow for a predictable architecture using the concept of isoreticular
design [30-33]. In the Cambridge Crystallographic Structure Databank, CCSD [34] six
compounds of Ca, Mg, Zn and Zr were established with the linear ligand 2',3',5',6'-
tetramethylterphenyl-4,4''-dicarboxylic acid (H2L) (Scheme 1) [35–40]. By solvothermal
reaction using H2L and Zn(NO3)2∙6H2O two ZnII complexes were synthesized, in which L2-
coordinates in different modes to generate a wavy 2D (4,4) network and in the other a planar
2D (4,4) network [36]. A mixed-ligand strategy was used in the synthesis of the mixed-ligand
coordination polymer {[Zn2(L)2(tib)]·DMF·10H2O}n (tib = 1, 3, 5-tris(1-imidazolyl)benzene)
in which the Zn atoms are connected by carboxylate groups to form paddle-wheel binuclear
secondary building units {Zn2(O2C-)4} within a 2D {Zn2(L)2} network. The tib ligands also
acts as a bidentate bridging ligand and links the {Zn2(L)2} network into a 3-fold
interpenetrating 3D framework [37]. As pillar linker H2L was used in the coordination
copolymerization of the ditopic linker BDC (1,4-benzenedicarboxylate) and the tritopic linker
TPA (4,4',4''-tricarboxylate-triphenylamine) to produce a non-interpenetrated pillared-layer
structure with the {Zn4O(O2CR)6} SBU [38]. From solvothermal reaction of Mg(NO3)2 and
H2L a 3D magnesium MOF of formula [Mg(L)(DMSO)]n with infinite 1D Mg chain SBUs
and coordinated DMSO molecules was obtained. These chains are linked via the carboxylate
groups of the L2– ligand into a 3D network. The Mg MOF shows good thermal and moisture
stability and can selectively adsorb CO2 over N2 [39]. From the mixture of the solvents
DMF/dioxane/H2O the calcium(II) framework {[Ca(L)(dioxane)]·2H2O}n was synthesized.
The central Ca2+ ion is eight-coordinated by six carboxylate oxygen atoms from four different
L2- molecules and two oxygen atoms from two coordinated dioxane molecules. Both
2

carboxylate groups of a L2- ligand are linked with two Ca2+ ions each to form 1D metal chains.
Further, each L2- ligand bridges two chains, forming a 3D framework [40].
Herein, we report the synthesis, characterization and crystal structures of seven
compounds based on the H2L ligand that include the solvate (H2L·2DMSO) (1·2DMSO), the
1D coordination polymer [Zn(L)(DMF)2]n (2), the two 2D coordination polymers
{[Zn(L)(DEF)]2·2DEF}n (3) and {[Co(L)(DEF)]2·2DEF}n (4), and the three mixed-ligand 3D
coordination polymers {[Zn2(L)2(BIBP)]·2DEF}n (5), {[Co2(L)2(BIBP)]·2DEF}n (6) and
{[Zn3(L)3(BIPY)1.5]·4DMF·1.5H2O}n (7) (where DMSO is dimethylsulfoxide, DMF is
dimethylformamide, DEF is diethylformamide, BIBP stands for 4,4′-bis(1-
imidazolyl)biphenyl, and BIPY denotes 4,4'-bipyridine) (Scheme 1).
O
OH
O
H2L, 1
HO
N
N
N
BIBP
BIPY
N
N
N
Scheme 1. The ligands used in the synthesis of the coordination networks 2-7.
2. Experimental
2.1. Materials and methods
All chemicals used for synthesis were of analytical grade, purchased commercially (mostly
from Sigma Aldrich) and used without further purification. The BIBP ligand was prepared
according to a reported procedure [41]. To obtain the linker H2L (1), 1,2,4,5-
o
tetramethylbenzene was first brominated in chloroform at 0 C, to give the brominated
compound 1,4-dibromo-2,3,5,6-tetramethylbenzene in about 96% yield. In the next step, a
Suzuki reaction between 1,4-dibromo-2,3,5,6-tetramethylbenzene and 4-carboxy-
phenylboronic acid afforded H2L in an overall yield of 67% [42]. CHN elemental analysis
was performed on a VarioELIII elemental analyzer. FT-IR spectra were recorded using a
Bruker Tensor 37 system equipped with an ATR unit (Platinum ATR-QL, Diamond) in the
4000-550 cm-1 region with 2 cm-1 resolution. The intensity of absorption bands is given as
strong (s), medium (m), broad (br) and weak (w). 1H and 13C spectra were recorded on Bruker
Avance DRX-200 and Bruker Avance DRX-500 instruments respectively. Thermogravimetric
3

analysis (TGA) was performed on a TG 209 F3 Tarsus. Nitrogen sorption experiments were
carried out with Quantachrome NOVA 4200 volumetric gas sorption instrument. Prior to N2
isotherm measurements at 77 K, the samples were outgassed at 180 °C under a vacuum of
10−3 mbar for 4 h. For the sorption measurements 20 to 40 mg of freshly synthesized samples
were weighed before and after the degassing procedure to confirm the evacuation of the
solvent.
2.2. Synthesis
2.2.1. Preparation of H2L·H2O (1·H2O )
To the solution of 1,4-dibromo-2,3,5,6-tetramethylbenzene (584 mg, 2.0 mmol) in
toluene (20 mL) in a 250 mL flask were added Na2CO3 (20 mL, 2 mol/L) and Pd(PPh3)4 (60
mg, 0.038 mmol) in toluene (5 mL). Through this mixture nitrogen was bubbled for 15 min.
4-Carboxyphenylboronic acid (730 mg, 2.2 mmol) dissolved in ethanol (20 mL) was added to
the flask with the mixture and nitrogen was continued to be bubbled through the solution for 5
more minutes. The mixture was refluxed during three days at 105 oC. Afterwards, the mixture
was evaporated till dryness. The residue was dissolved in water (50 mL) and the pH was
adjusted to ~2 with HCl (conc.) The desired product was extracted with ethyl acetate (3x100
mL). The organic layer was dried over Na2SO4, and the solvent was removed in vacuum.
Recrystallization from tetrahydrofuran/methanol gave the desired product. Yield: 527.2 mg
(67%); M.p. - not melting, dec. ~300oC. Elemental analysis calcd (%) for C24H22O4∙H2O
(M.W. 392.44), C 73.45, H 6.16; found C 73.97, H 6.31 %. 1H NMR (DMSO-d6): δ = 1.88 (s;
12H, CH3), 7.29 (d; 4H, aromatic-CH), 8.06 (d; 4H, aromatic-CH), 13.00 (s; 2H, COOH).
FTIR (cm-1; ATR): ν = 2991(w), 2954(w), 2877(w), 2654(w), 2538(w), 2285(w), 2102(w),
1942(w), 1830(w), 1679(s), 1607(s), 1563(w), 1515(w), 1462(w), 1420(s), 1383(w),
1312(s),1291(s), 1277(s), 1177(m), 1138(w), 1125(w), 1103(w), 1014(w), 994(m), 944(m),
879(m), 838(w), 811(w), 769(s), 740(w), 708(m), 676(w), 666(w). Single crystals of H2L for
structural study were obtained by recrystallization from DMSO as 1·2DMSO.
2.2.2. [Zn(L)(DMF)2]n (2).
Zn(NO3)2∙6H2O (59.5 mg, 0.2 mmol), H2L (39.2 mg, 0.1 mmol) and 1,2,4-triazole (5.6
mg, 0.05 mmol) were mixed in dimethylformamide (DMF, 10 mL) and homogenized by
stirring for 2 h. The slurry was heated to 120 oC in a Teflon-lined stainless-steel bomb reactor
for 48 h to obtain a white microcrystalline precipitate. The product was washed with DMF
and ethanol and dried in an oven at 100 oC. Yield: 45 mg (77%). Elemental analysis calcd (%)
4

for C30H34N2O6Zn (M.W. 583.96) C 61.70, H 5.87, N 4.79; found C 61.61, H 5.47, N 4.59.
FTIR (cm-1; ATR): ν = 3104(w), 2924(w), 1664(m), 1596(s), 1550(m),1515(s), 1403(s),
1391(s ), 1375(s), 1304(m), 1275(m), 1215(w), 1197(w), 1176(m), 1151(m), 1091(m),
1071(m), 1040(w), 1021(w), 1004(m), 989(w), 877(m), 857(m), 775(s), 757(w), 714(m),
679(w).
2.2.3. {[Zn(L)(DEF)]2·2DEF}n (3).
A mixture of Zn(NO3)2∙6H2O (59.5 mg, 0.2 mmol) and H2L (39.2 mg, 0.10 mmol) was
dissolved in diethylformamide (DEF, 10 mL) in a 100 mL glass flask. The flask was placed in
a 90 oC oil bath and heated for 96 h. Colorless crystals were collected and washed with DEF.
Yield: 93 mg (73%); Elemental analysis calcd (%) for C68H84N4O12Zn2 (M.W.1280.13) C
63.80, H 6.61, N 4.38; found C 63.75, H 6.55, N 4.31. FTIR (cm-1; ATR): ν = 3677(w),
3144(w), 2989(s), 2973(s), 2902(s), 1653(s), 1596(s), 1548(m), 1439(m), 1407(s), 1394(s),
1384(s), 1277(w), 1253(m), 1232(w), 1174(w), 1100(m), 1075(s), 1066(s), 1058(s), 1019(m),
989(w), 880(w), 858(w), 779(s), 753(w), 714(m), 676(w).
2.2.4. {[Co(L)(DEF)]2·2DEF}n (4).
A mixture of Co(NO3)2∙6H2O (58.2 mg, 0.2 mmol) and H2L (39.2 mg, 0.1 mmol) was
o
dissolved in DEF (10 mL) in a 100 mL glass flask. The flask was placed in a 90 C oil bath
and heated for 96 h. Pink crystals were collected and washed with DEF. Yield: 92 mg (73%);
Elemental analysis calcd (%) for C68H84N4O12Co2 (M.W.1267.25) C 64.45, H 6.68, N 4.42;
found C 64,38, H 6.61, N 4.38. FTIR (cm-1; ATR): ν = 3677(w), 3231(w), 2989(s), 2973(s),
2902(s), 1636(m), 1583(s), 1529(m), 1450(m), 1405(s), 1394(s), 1383(s), 1251(m), 1242(w),
1232(w), 1174(w), 1075(s), 1066(s), 1057(s), 1028(m), 943(w), 892(w), 879(w), 794(w),
777(s), 743(w), 711(w). This compound showed a BET surface area 28 m²/g.
Single crystal synthesis of 3 and 4 for structure determination. A mixture of
M(NO3)2∙6H2O (29.8 mg, 0.10 mmol) (M = Zn or Co) and H2L (19.6 mg, 0.05mmol) was
dissolved in DEF (2.0 mL) in a 4 mL vial. The vial was tightly capped with a Teflon-lined
cap, placed in a 90 oC oven and heated for 96 h.
2.2.5. {[Zn2(L)2(BIBP)]·2DEF}n (5).
A mixture of BIBP (14.3 mg, 0,05 mmol) and H2L (19.6 mg, 0,05 mmol) was
dissolved in 3 mL or DEF at moderate heating in a 12 mL screw-capped glass test tube. To
this ligand solution was added Zn(NO3)2·6H2O (29.9 mg, 0.1 mmol) dissolved in 2 mL of
5

DEF. The mixture was heated at 120 °C for 24 h, then cooled to room temperature at the rate
of 5 °C/h. Colorless crystals were collected and washed three times with 3 mL of DMF and
three times with 3 mL of ethanol. The crystalline product was dried in air at room
temperature. Yield: 31.3 mg (92%). Elemental analysis calcd (%) for C76H76N6O10Zn2
(M.W.1364.23): C 66.91, H 5.62, N, 6.16; found C 66.50, H 5.76, N, 5.78. FTIR (cm-1; ATR):
ν = 3135(w), 2976(w), 2338(w), 1670(m), 1609(s), 1554(m) 1519(s), 1435(m), 1399(s),
1363(s), 1311(m), 1260(m), 1172(w), 1129(m), 1094(m), 1064(s), 1018(w), 1007(w), 992(w),
964(m), 945(w), 901(w), 880(w), 845(m), 821(m), 795(w), 780(s), 753(w), 713(m), 675(w).
2.2.6. {[Co2(L)2(BIBP)]·2DEF}n (6).
A mixture of BIBP (14.3 mg, 0.05 mmol) and H2L (19.6 mg, 0.05 mmol) was
dissolved in 3 mL of DEF with moderate heating in a 12 mL screw-capped glass test tube. To
this ligand solution was added Co(NO3)2·6H2O (29.1 mg, 0.1 mmol) in 2 mL of DEF. The
mixture was heated at 120 °C for 24 h then cooled to room temperature at the rate of 5 °C/h.
Pink crystals were collected and washed three times with 3 mL of DMF and three times with
3 mL of ethanol. The crystalline product was dried in air at room temperature. Yield: 32. 1 mg
(95%). Elemental analysis calcd (%) for C76H76N6O10Co2 (M.W. 1351.32): C 67.55, H 5.67,
N 6.22; found C 67.38, H 5.61, N 6.17. FTIR (cm-1; ATR): ν = 3132(w), 2971(w), 1666(m),
1607(s), 1549(m), 1516(s), 1434(sh), 1402(s), 1309(m), 1290(w), 1279(w), 1257(m),
1217(w), 1177(w ), 1130(w), 1105(m), 1063(m), 1021(w), 1005(w), 991(w), 964(w), 944(w),
878(w), 856(m), 844(m), 821(m), 776(s), 750(m), 712(w), 688(w), 673(w).
2.2.7. {[Zn3(L)3(BIPY)1.5]·4DMF 1.5H2O}n (7).
Zn(NO3)2∙6H2O (59.5 mg, 0.2 mmol), H2L∙(39.2 mg, 0.1 mmol) and 4,4-BIPY (5.6
mg, 0.05 mmol) were mixed in DMF (10 mL) and homogenized by stirring for 2 h. The slurry
was heated to 120 °C in a Teflon-lined stainless-steel bomb reactor for 48 h to obtain a white
microcrystalline precipitate. The product was washed with DMF and ethanol and dried in an
oven at 100 oC. Yield: 90 mg (71%). Elemental analysis calcd (%) for C67H71N5O12Zn2 (M.W.
= 1269.03) C 63.41, H 5.64, N 5.52; found C 63.34, H 5.57, N 5.49. FTIR (cm-1; ATR): ν =
2988(w), 1674(w), 1609(s), 1587(s), 1536(s), 1493(w), 1403(s), 1277(w), 1255(w), 1225(m),
1175(w),1131(w), 1096(w), 1075(m), 1049(w), 1019(w), 990(w), 877(w), 854(m), 818(m),
796(w), 777(s), 755(w), 727(w), 714(m), 675(w).
6

2.3. X-ray crystallography
Experimental data for 1·2DMSO, 2, 3’, 4 and 7 were collected on a Bruker APEX DUO with
APEX II CCD area detector, equipped with microfocus sealed tube, Mo-Kα (λ = 0.71073 Å)
or Cu-Kα (λ = 1.54178 Å) radiation and multilayer mirror monochromator and for 3, 5 and 6
on an Xcalibur E CCD diffractometer (graphite monochromator) using MoKα radiation, ω-
and ϕ-scan. Data collection on the Bruker APEX DUO diffractometer has been carried using
Apex2 [43], cell refinement and data reduction with SAINT [44], experimental absorption
correction with SADABS [45], and on the Xcalibur with CrysAlis [46].
For compound 7 the data set was initially tried to refine with the solvent molecules of
crystallization, revealing the presence of about four DMF and 1.5 water molecules per
{Zn3(L)3(BIPY)1.5} formula unit. As refinement for the crystal solvent was unsatisfactory, and
also in view of the low data set quality which is common for MOF structures, the SQUEEZE
option as implemented in PLATON [47] was used. A total of 1111 electrons were found (and
squeezed) in the solvent accessible volume of 4521 Å3 (within the unit-cell volume of 10372
Å3) with a void probe radius of 1.2 Å.
Final unit cell dimensions for 1 – 7 were obtained and refined on the entire data set. All
calculations necessary to solve the structures and to refine the proposed model were carried
out with the SHELX program [48]. Non-hydrogen atoms were treated anisotropically (full-
matrix least squares method on F2). Carbon bonded H atoms were placed in calculated
positions and were treated using riding model approximations with Uiso(H) = 1.2Ueq(C),
while the oxygen bonded H-atoms were found from differential Fourier maps at an
intermediate stage of the refinement, and their positions were constrained using the AFIX 83
instruction in SHELX. These hydrogen atoms were refined with the isotropic displacement
parameter Uiso(H) = 1.5Ueq(O).
The X-ray data and the details of the refinement for 1 – 7 are summarized in Table S1, the
selected bond lengths (Å) and angles (deg) in coordination metal environment in 2 – 7 are
given in Table S2 and S3, and hydrogen-bonding geometry in 1 – 7 in Table S5 in the
Supplementary material.
3. Results and discussion
3.1. Synthesis
7

From the reaction of H2L (1) and zinc(II) or cobalt(II) nitrate under solvothermal conditions
o
(T = 90 C, t = 96 h, DEF as solvent) the 2D coordination polymers of composition
{[Zn(L)(DEF)]2·2DEF}n (3) and {[Co(L)(DEF)]2·2DEF}n (4) were synthesized. In the
presence of a weak base such as 1,2,4-triazole under the same solvothermal conditions (T =
o
90 C, t = 96 h), but using DMF as solvent a 1D-coordination polymer with composition
[Zn(L)(DMF)2]n (2) was obtained. The 1,2,4-triazole did not participate in the formation of
coordination polymer. The interaction of H2L with Zn and Co nitrate salts in the presence of
o
BIBP under solvothermal conditions (T = 120 C, t = 24 h, DEF as solvent) led to formation
of 3D coordination polymers with composition {[Zn2(L)2(BIBP)]·2DEF}n (5) and
{[Co2(L)2(BIBP)]·2DEF}n (6). By using BIPY under solvothermal conditions (T = 120 oC, t =
48 h, DMF as solvent) the 3D coordination polymer {[Zn3(L)3(BIPY)1.5]·4DMF·1.5H2O}n (7)
was formed.
3.2 IR-spectra.
The FTIR spectra of the materials are very similar and are given in Figures S1–S7,
Supplementary material. The spectra show moderate intense bands between 3300 cm−1 and
2902 cm−1 that may be assigned to asymmetric and symmetric C–H stretching of the aromatic
aryl rings. Broad bands between 3600 and 3200 cm−1 correspond to asymmetric and
symmetric O–H stretching vibrations of water molecules. The strong absorption peaks at
1679–1583 cm−1 can be associated with asymmetric COO− vibration, and peaks at 1312–1391
cm−1 with symmetric COO− vibration of the carboxylate groups [49]. The strong bands
between 1609 cm−1 and 1540 cm−1 may be assigned to C=C stretching of the aromatic aryl
rings. The absorption bands in the IR spectra of 4 and 5 at 1064 and 964 cm−1 indicate the
presence of N-substituted imidazole rings. Because the stretching vibrations of the
carboxylate groups and the characteristic stretching vibrations of the imidazole rings and
phenyl rings both appear at 1550–1700 cm−1 and overlap partially, the absorption bands in
this region are comparatively broad. A single absorption band at 845 cm−1 might be attributed
to the bending vibration of a para-substituted benzene ring [49].
3.3 Thermogravimetric analysis
In order to assess the thermal stability of the coordination architecture of compounds 1–7,
thermogravimetric analyses (TGA) were carried out on the crystalline materials in air at a
heating rate of 5 °C/min in the temperature range of 30–1000 °C (Figures S8-S14,
Supplementary material). From its synthesis the ligand was obtained with one molecule of
8

solvent water as H2L·H2O (1·H2O). During the thermogravimetric analysis H2L·H2O loses
this one molecule of water at ~100 °C (found 4.5 wt.%, calc. 4.6 wt.%) and is then stable up
to 350 °C, after which a rapid decomposition occurs. Compound 2 is stable up to 160 °C, and
after losing of two DMF molecules (found 25 wt.%, calc. 25.0 wt.%) at 160-200 °C it remains
stable up to 340 °C, after which the coordination polymer decomposes. For complexes 3 and
4, the initial weight loss of ~16 wt.% before 320 °C is due to the release of two coordinated
DEF molecules (calc. 15.8 wt.% and 16.0 wt.%, respectively). The second weight loss occurs
in the temperature range of 320–450 °C, and is ascribed to the release of the L2- ligand from
the framework. The TGA investigations of the isostructural compounds 5 and 6 indicate a
gradual weight loss of ~15 wt.% in the temperature range of 100-300 °C, which is due to the
release of the two non-coordinated DEF molecules (calc. 14.8 wt.% and 15.0 wt.%,
respectively). The second weight loss of ~70 wt.% occurs in the temperature range of 350–
500 °C, and is attributed to the release of the BIBP co-ligand and the L ligand from the
framework. Compound 7 is stable up to 100 °C after which it loses 18.3 wt.% of solvent (calc.
18.7 wt.%) up to 180 °C, and reaches a plateau until 380 °C, where the structure collapses.
The solvent-depleted coordination polymers 2-7 are mostly stable until at least 300 °C, except
for 4 which start to decompose around 250 °C.
3.4 Gas sorption studies
Compounds 3-7 contain non-coordinated solvent of crystallization. This solvent was tried to
remove by activating 20-40 mg of sample through heating at 180 °C under vacuum of 10−3
mbar for 4 h. Figure S15-S19 in the Supplementary Material present the N2 sorption curves
for the activated compounds. The Brunauer-Emmett-Teller (BET) surface areas (SBET) of the
activated 2D networks were calculated for 3 as SBET = 145 m2/g and for 4 with SBET = 28
m2/g. For the pillar-layer frameworks 5 and 6 with BIBP as coligand the surface areas are 83
and 19 m2/g, respectively. In the 3D framework 7 the surface area was 66 m²/g. Overall, these
surface areas are low with surfaces areas below 30 m2/g being even in the range of the outer
surface area of a fine powder. From the TGA studies, heat-vacuum activation under the used
conditions should have been successful to sufficiently remove even low volatile DEF and
DMF solvent of crystallization. Evidently, the solvent-depleted networks are not stable and
collapse.
3.5 Structural characterization
9

Compound [Zn(L)(DMF)2]n (2) crystallizes in monoclinic space group C2/c (Table S1,
Supplementary material). The asymmetric unit comprises one half of a zinc atom located on
the twofold rotation axis, one half of the L2- ligand which resides on an inversion center and
one DMF molecule. The zinc atom adopts a tetrahedral O4 surrounding due to coordination of
two DMF molecules and two fully deprotonated monodentate L2˗ ligands (Fig. 1). The
interatomic distances Zn1–O1 and Zn1–O3 are 1.935(1) and 1.979(2) Å, respectively, O-Zn-
O angles cover the range 100.30(8) – 119.08(7)° (Table S2, Supplementary material). The
orientation of the DMF molecules is stabilized by intramolecular C–H···O2 3.122 Å (H···O
2.36Å, CHO 139) interactions (Table S5, Supplementary material). The dicarboxylate
ligand bridges the zinc atoms and both form a zigzag-like chain along the (-101)
crystallographic direction with coplanar arrangement of metal atoms and carboxyphenyl
moieties (Fig. 1). The Zn···Zn separation through the L2- ligand along the chain equals 19.5 Å
and the Zn···Zn···Zn angle is 116.1°. The carboxyphenyl fragments of the ligand are coplanar
and form a dihedral angle of 72.8° with the central tetramethylphenyl moiety. In the crystal
the parallel chains are united in supramolecular layers parallel to the (101) crystallographic
plane by inter-chain C–H···O2 (x, y+1, z) interactions with parameters H···O 2.50, C···O
3.200 Å, CHO 137, shown in Fig. 2a. Between these parallel layers only van der Waals
interactions are observed (Fig. 2b).
Fig. 1. View of the 1D coordination polymer in 2 with partial atomic numbering scheme (50%
thermal ellipsoids).
10

a
b
Fig. 2. Fragment of the crystal packing of 2 to illustrate (a) the formation of the supramole-
cular layer parallel to the (101) plane and (b) the parallel arrangement of layers; hydrogen
atoms in (b) were omitted for clarity.
The two isostructural compounds 3 and 4 with composition {[Zn(L)(DEF)]2·2DEF}n
and {[Co(L)(DEF)]2·2DEF}n, crystallize in the monoclinic space group C2/c (Table S1,
Supplementary material). The asymmetric part of unit cell of these compounds contains one
Zn or Co atom, two-halves of the L2- ligands, one of which resides on an inversion center and
another one on a two-fold axis, together with one coordinated and one crystal solvent DEF
molecule (Fig. 3a). The carboxyphenyl fragments and central tetramethylphenyl moiety of the
L2- ligands form dihedral angles close to perpendicular (82.2–89.0°). The structure of 3 has
been described earlier [38], but we have repeated the structural study of this compound at two
temperatures: 293 (3) and 95 K (3’).
The secondary building unit of the metal and ligand donor atoms is the dinuclear
paddle-wheel unit. Thus, metal atoms are five coordinated with slightly distorted square
pyramidal coordination geometry by four oxygen atoms from carboxylate groups of four L2-
in the base of pyramid and one oxygen from DEF in axial position. The Addison parameter 
[50] equals 0.008, 0.003 and 0.008 in 3, 3’ and 4, respectively (τ = 1 for an ideal trigonal
bipyramid and τ = 0 for an ideal square pyramid). The Zn–O distances fall in narrow range of
1.979(3) – 2.062(3) Å at 293 K (for 3) and of 1.980(3) – 2.061(3) Å at 95 K (for 3’). The Co–
O distances are in the range of 1.999(6) – 2.085(6) Å (for 4, Table S2, Supplementary
material). The linker L2- acts as (κ1-κ1)-(κ1-κ1)-μ4 bridge to connect four metal atoms.
Together, the ligands link the dinuclear paddle-wheel units to form a (4,4) 2D square lattice
(sql) (Fig. 3b). The sql layers are parallel to the (-102) crystallographic plane, separated by
the terminal DEF axial ligands and DEF crystal-solvent guest molecules, and stack in
11

ABABAB… fashion along the crystallographic c axis (Fig. 3c). The metal···metal separation
in the dinuclear moiety equals 2.949(1)/2.950(1) Å in 3 and 3’ at room and low temperature,
respectively, and 2.828(3) Å in 4 (Table S2, Supplementary material). The distances between
the centroids of the paddle-wheel units in the square lattice across the L ligands are 19.4 and
19.5 Å, 19.5 and 19.5 Å, and 19.4 and 19.5 Å, and the distances between mean planes of the
layers equal 4.6, 4.4 and 4.5 Å in 3, 3’ and 4, respectively. The comparison of room and low
temperature data shows that the metrics of the sql net is slightly dependent on temperature,
while the distance between the mean planes of the grids vary by about 2%, which is in a good
agreement with the difference in the unit cell parameter c. Only weak C–H···O interactions
have been found in the structures of 3 and 4 between the grids and between the grids and
solvent DEF molecule (Table S5, Supplementary material). Without the solvent molecules
open channels would be formed between the grids (Fig. 3d) which are at least partially
retained upon activation as seen from the N2 sorption measurements which gave a BET
surface area of 145 m2/g for 3.
a
b
c
d
Fig. 3. (a) [M2(L)4(DEF)2] dinuclear unit in 4 (isostructural to 3 with M = Zn) with partial
atomic numbering scheme (50% thermal ellipsoids). (b) Fragment of a 2D sql coordination
polymer. (c, d) Stack of parallel layers with (c) and without (d) the DEF crystal solvent shown
in space filling mode.
12

The total solvent accessible void volume for 3, 3’ and 4 was calculated by PLATON
[47] upon removal of the solvent DEF molecules and equals 28, 27 and 27 % of the total unit
cell volume, respectively.
In 3 and 4 the paddle-wheel dinuclear units serve as four-connected square nodes with
terminal axial ligands and the carboxylate C atoms serve as sole points of extension, resulting
in the 2D grid-like sql structure. These 2D nets may be used to generate 3D porous MOFs via
“pillaring” of these layered structures by bridging the axial metal sites of the paddle-wheel
moieties [51]. The terminal ligands at the SBU can be replaced by a ditopic ligand, typically a
nitrogen donor, and the paddle-wheel binuclear units then serve as six-connected octahedral
6-c nodes resulting in 3D mixed-ligand MOFs [52].
We used this strategy to transform the 2D coordination polymers 3 and 4 into 3D
MOFs by addition of BIBP or BIPY as N,N-exo-bidentate rigid ligands into the reaction
mixture. The latter replace the terminal axial DEF ligands and result in the 3D and three-fold
interpenetrated frameworks {[Zn2(L)2(BIBP)]·2DEF}n (5), {[Co2(L)2(BIBP)]·2DEF}n (6) and
{[Zn2(L)2(BIPY)]·4DMF·1.5H2O}n (7). Remarkably, the BIBP pillar yields bsn (beta-Sn)
topology, the BIPY pillar pcu (primitive cubic, -Po) topology.
The two isostructural and isomorphic compounds 5 and 6 crystallize in the monoclinic
space group C2/c and have nearly identical unit-cell parameters, (Table S1, Supplementary
material). The asymmetric part of the unit cell comprises one Zn or Co atom, two-halves of
the L2- ligands, one-half of the BIBP ligand and one DEF solvent molecule (Fig. 4a). Similar
to 3 and 4 one of the L2- ligands resides on an inversion center and another one on the two-
fold axis and both form a square lattice, sql network for the {M(L)2}n substructure (Fig. 5b).
Compared with 3 and 4, the structures of 5 and 6 demonstrate some difference in the
formation of the paddle-wheel dinuclear unit. Two symmetry independent L2- ligands reveal
different coordination modes (κ1-κ1)-(κ1-κ1)-μ4 and (κ2-κ1)-(κ2-κ1)-μ4. For the first
coordination mode the Zn–O and Co–O distances equal 2.016(2) and 2.023(3) Å, while for
second one they are in the range 2.085(2) – 2.492(3) and 2.087(3) – 2.299(3) Å (Table S3 in
Supp. Inf.), respectively. It should be mentioned unusual (κ2-κ1) bridging function of
carboxylic group in paddle-wheel unit for second coordination mode which is more
pronounced in 5 and 6: one of the oxygen atoms of carboxylic group serves as a bridge
between two metal atoms with Zn–O distances 2.085(2) and 2.492(2) Å, and Co–O 2.087(3)
and 2.298(3) Å. The survey of CSD did not reveal so short second metal – oxygen atoms
contacts in paddle-wheel (Zn2/Co2) units. The shortest second metal–oxygen atoms contacts
13

observed before are 2.648 Å [53] and 2.780 Å [54] for Co2 and 2.805 Å [55] for Zn2 units,
respectively. The couples of the ligands with the identical coordination mode in 5 and 6 are
trans-situated with respect to the couple of two-fold related metal atoms and unite them in
distorted paddle-wheel dinuclear SBUs with molecular symmetry essentially different from
C4 (Fig. 5c). The metal atoms are five coordinated with square pyramidal coordination
geometry,  = 0.019 and 0.012 [50].
The interatomic distances Zn···Zn/Co···Co in the dinuclear SBU core equal to
3.0134(6) and 2.931(1) Å, being longer than in 3, 3’ and 4. The distances between the
centroids of the dinuclear moieties in the square lattice across the dicarboxylic ligands equal
19.1 and 19.5 Å, and 19.1 and 19.5 Å, for 5 and 6, respectively. The slightly larger difference
between each of the two values when compared with 3, 3’ and 4 is related with the diverse
coordination modes for the two unique ligands in 5 and 6. The ditopic BIBP ligands
coordinate at the axial position of the square-pyramidally coordinated metal atoms (Zn–N
2.008(2), Co–N is 2.045(4) Å, Table S3 in Supplementary material). This completes their
distorted octahedral NO5 surrounding, and unite the square {Zn2(L)2} grids to provide a
pillared-layer 3D framework with bsn topology (Fig. 5b) [52]. The distance between the mean
planes of the layers separated by the BIBP ligands as pillars equals to 14.2 and 14.1 Å for 5
and 6, respectively. The crystal structures of 5 and 6 displays a 3-fold parallel interpenetration
of the networks (Fig. 5d). Despite the interpenetration, the resulting structure still possesses
potential porosity in the form of isolated and solvent-filled cavities. These cavities are filled
with DEF crystal solvent molecules (Fig. 5e). Upon omitting these DEF molecules, the total
solvent accessible volume for 5 and 6 was calculated by PLATON to 2025.5 and 2021.7 Å3
[47] or 29% of the total unit cell volume.
a
b
c
14

d
e
Fig. 5. (a) View of the [Zn2(L)4(BIBP)2] dinuclear units in 5 (isostructural with 6) with atomic
numbering scheme (50% thermal ellipsoids). (b) Section of a single 3D framework with bsn
(beta-Sn) topology. (c) SBU in the structures of 5. Green double arrow shows the position of
two-fold axis. (d) Fragment of the crystal packing to illustrate the three-fold interpenetration
of the 3D networks in 5, by depicting only the connectivity of the Zn2 centroids, with (e)
showing also the solvent DEF molecules in space filling mode.
Compound 7 with the formula {[Zn3(L)3(BIPY)1.5]·4DMF·1.5H2O}n crystallized in
the monoclinic non-centrosymmetric space group C2 (Table S1 in Supp. Inf.). The
asymmetric unit contains three Zn atoms, three L2- and one and a half BIPY ligands, together
with about 4 DMF and 1.5 water molecules as solvates. For the final structure solution the the
SQUEEZE option as implemented in PLATON [49] was used. The L2– ligands in the structure
of 7 act as (κ1-κ1)-(κ1-κ1)-μ4 bridges and form two symmetry-independent dinuclear paddle-
wheel units [Zn2(O2C)4(NBIPY)2]. One of them resides around the two-fold axis (Fig. 6a) and
another one in a general position (Fig. 6b). Each SBU gives rise to its own, independent 3D
framework. The zinc atoms are five coordinated with a distorted square-pyramidal NO4
surrounding. The Zn···Zn distances in the two different paddle-wheel units almost coincide
with 2.890(2) and 2.893(1) Å. The Zn–O distances are in the range 2.002(8)–2.093(8) Å, and
Zn–N 2.2011(6)–2.033(6) Å. Metal atoms are five coordinated with square pyramidal
coordination geometry (the parameter of distortion  equals 0.045, 0, and 0.028 for Zn(1),
Zn(2) and Zn(3), respectively). Linked through the dicarboxylate ligands the paddle-wheel
units form sql grids parallel to the (ab) crystallographic plane. Similar to the structures of 5
and 6, these grids are connected by the BIPY ligands to result in 3D frameworks albeit now
with pcu (α-Po) topology (Fig. 6c). The crystal structure comprises three such frameworks
with parallel interpenetration (Fig. 6d). Two symmetry-independent frameworks are based on
the two symmetry-independent SBUs, the third one is generated by symmetry from the SBU
with Zn2 and Zn3 (Fig. 6b). The distances between the centroids of the dinuclear moieties in
15

the square grid and the distances between the mean planes of the square grids separated by
BIPY ligands as pillars adopt the same value in the symmetry independent 3D frameworks
with 19.4 and 13.9 Å, respectively, irrespective of the conformational difference in the
bridging ligands.
a
b
c
d
Fig. 6. View of the symmetry independent [Zn2(L)4(BIPY)2] dinuclear paddle-wheel units in 7
with partial atomic numbering scheme (50% thermal ellipsoids). (a) Paddle-wheel units on
two-fold axis and (b) in general position. (c) 3D framework with pcu (primitive cubic, α-Po)
topology and (d) three-fold interpenetration of frameworks in crystal of 7, blue and red
coloured frameworks are symmetry related and the green one is symmetry independent in the
crystal structure. The crystal solvent molecules were omitted for clarity.
In the three crystallographically independent L2– ligands in 7 the three phenyl rings are
not coplanar. The peripheral phenyl rings form mutual dihedral angles of 16.2, 9.2 and 32.7,
between each other. Further, the peripheral and the central phenyl rings are again closer to
16

perpendicular to each other, with dihedral angles of 75.9 and 88.3°, 83.7 and 75.8, and 71.2
and 76.1. In the BIPY ligands the pyridine rings form dihedral angles 39.0 and 37.9.
Also, the three-fold interpenetrated framework in 7 results in a potentially porous
structure. The pore volume in 7 is filled by ordered and disordered solvent DMF and water
molecules. Based on the solvent-depleted structure, the total solvent accessible volume in 7
was calculated by PLATON [47] to 4081.7 Å3 or 39% of the total unit cell volume.
4. Conclusions
We have synthesized six new coordination polymers based on a tetramethylterphenyl-
dicarboxylic acid. Compound [Zn(L)(DMF)2]n (2) is a 1D polymer in which the deprotonated
ditopic tetramethyl-terphenyldicarboxylate ligand acts as a bridge to connect two zinc atoms.
Compounds {[M(L)(DEF)]2·2DEF}n (M = Zn, 3 and M = Co, 4) are isostructural, and the
tetradentate terphenyldicarboxylate ligand coordinates to four metal atoms to form paddle-
wheel SBUs which are interconnected in 2D sql coordination polymers. In the isostructural
compounds {[M2(L)2(BIBP)]·2DEF}n (M = Zn, 5 and M = Co, 6) the sql coordination grids
are pillared by BIBP ligands into 3D and three-fold interpenetrated frameworks of bsn
topology. When the BIPY ligand serves as pillar a 3D and three-fold interpenetrated
framework of pcu (-Po) topology has been found in structure of
{[Zn3(L)3(BIPY)1.5]·4DMF·1.5H2O}n (7). The present results suggest that the assembly of the
ditopic tetramethyl-terphenyldicarboxylate ligand with other metals will attract even more
attention to us. In order to synthesize porous coordination polymers we plan to apply shorter
nitrogen-containing neutral ligands, which will act as pillars such as 1,4-
diazabicyclo[2.2.2]octane or pyrazine to avoid the interpenetration and increase the stability
of the framework upon activation, that is in the absence of solvent of crystallization.
Acknowledgement
The financial support of European Social Fund for Regional Development, Competitiveness
Operational Programme Axis 1 – Project “Novel Porous Coordination Polymers with Organic
Ligands of Variable Length for Gas Storage”, POCPOLIG (ID P_37_707, Contract
67/08.09.2016, cod MySMIS: 104810) is gratefully acknowledged.
Appendix A. Supplementary material
17

Crystallographic data for compounds 1 - 7 have been deposited with the Cambridge
Crystallographic Data Center, CCDC 1939645 (1), 1939640 (2), 1939639 (3), 1939646 (3’),
1939641 (4), 1939642 (5), 1939643 (6), 1939644 (7). Copies of this information may be
obtained from The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: +44-
1233-336033; e-mail: deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk ).
Supplementary data (IR-spectra, TGA curves, sorption isotherms and crystallographic details
of compounds 1-7) can be found, in the online version, at http://
References
[1] H.-C. Zhou, J.R. Long, O.M. Yaghi, Chem. Rev. 112 (2012) 673.
[2] V. Guillerm, D. Kim, J.F. Eubank, R. Luebke, X. Liu, K. Adil, M.S. Lah, M. Eddaoudi,
Chem. Soc. Rev. 43 (2014) 6141.
[3] J.R. Long, O.M. Yaghi, Chem. Soc. Rev. 38 (2009) 1213.
[4] S. Kitagawa, S. Natarajan, Eur. J. Inorg. Chem. (2010) 3685.
[5] M. Yoon, R. Srirambalaji, K. Kim, Chem. Rev. 112 (2012) 1196.
[6] D. Farrusseng, S. Aguado, C. Pinel, Angew. Chem. Int. Ed. 48 (2009) 7502.
[7] J. Lee, O. K. Farha, J. Roberts, K.A. Scheidt, S.T. Nguyen, J.T. Hupp, Chem. Soc. Rev. 38
(2009) 1450.
[8] R.B. Getman, Y.-S. Bae, C.E. Wilmer, R.Q. Snurr, Chem. Rev. 112 (2012) 703.
[9] Z. Chen, S. Xiang, H. D. Arman, P. Li, S. Tidrow, D. Zhao, B. Chen, Eur. J. Inorg. Chem.
(2010) 3745.
[10] F. Ma, S. Liu, D. Liang, G. Ren, C. Zhang, F. Wei, Z. Su, Eur. J. Inorg. Chem. 24 (2010)
3756.
[11] Z. Zhang, Y. Zhao, Q. Gong, Z. Li, J. Li, Chem. Commun. 49 (2013) 653.
[12] J.-R. Li, Y. Ma, M.C. McCarthy, J. Sculley, J. Yu, H.-K. Jeong, P.B. Balbuena, H.-C.
Zhou, Coord. Chem. Rev. 255 (2011)1791.
[13] J.-R. Li, J. Sculley, H.-C. Zhou, Chem. Rev.112 (2012) 869.
[14] S.K. Henninger, F. Jeremias, H. Kummer, C. Janiak, Eur. J. Inorg. Chem. (2012) 2625.
[15] C. Janiak, S.K. Henninger, Chimia 67 (2013) 419.
[16] P. Küsgens, M. Rose, I. Senkovska, H. Fröde, A. Henschel, S. Siegle, S. Kaskel,
Micropor. Mesopor. Mater. 120 (2009) 325.
[17] J. Ehrenmann, S.K. Henninger, C. Janiak, Eur. J. Inorg. Chem. (2011) 471.
[18] S.K. Henninger, H.A. Habib, C. Janiak, J. Am. Chem. Soc. 131 (2009) 2776.
18

[19] G. Akiyama, R. Matsuda, S. Kitagawa, Chem. Lett. 39 (2010) 360.
[20] G. Akiyama, R. Matsuda, H. Sato, A. Hori, M. Takata, Micropor. Mesopor. Mater. 157
(2012) 89.
[21] C. Janiak, S.K. Henninger, Nachr. Chemie 61 (2013) 520.
[22] F. Jeremias, V. Lozan, S.K. Henninger, C. Janiak, Dalton Trans. 42 (2013) 15967.
[23] F. Jeremias, D. Fröhlich, C. Janiak, S.K. Henninger, New J. Chem. 38 (2014) 1846.
[24] F. Jeremias, D. Fröhlich, C. Janiak, S.K. Henninger, RSC Adv. 4 (2014) 24073.
[25] C. Janiak, Dalton Trans. (2003) 2781.
[26] C. Janiak, J.K. Vieth, New J. Chem. 34 (2010) 2366.
[27] G. Férey, Chem. Soc. Rev. 37 (2008) 191.
[28] N. Stock, S. Biswas, Chem. Rev. 112 (2012) 933.
[29] (a) S. Kitagawa, R. Kitaura S. Noro, Angew. Chem. Int. Ed. 43 (2004) 2334; (b) S.
Kitagawa, R. Kitaura S. Noro, Angew. Chem. 116 (2004) 2388.
[30] M. Eddaoudi, J. Kim, N. Rosi, D. Vodak, J. Wachter, M. O'Keeffe, O.M. Yaghi, Science.
295 (2002) 469.
[31] D.J. Tranchemontagne, Z. Ni, M. O'Keeffe, O.M. Yaghi, Angew. Chem. Int. Ed. 47
(2008) 5136.
[32] (a) O. Delgado Friedrichs, M. O'Keeffe, O.M. Yaghi, Acta Crystallogr. A59 (2003) 22;
(b) M. O’Keeffe, M.A. Peskov, S.J. Ramsden, O.M. Yaghi, Acc. Chem. Res. 41 (2008)
1782.
[33] M. O'Keeffe, O.M. Yaghi, Chem. Rev. 112 (2012) 675.
[34] F.H. Allen, O. Kennard, Cambridge Crystallographic Data Base. Chem. Design Automat.
News. 8 (1993) 31.
[35] H.-L. Jiang, D. Feng, T.-F. Liu, J.-R. Li, H.-C. Zhou, J. Am. Chem. Soc. 134 (2012)
14690.
[36] X.-L. Zhao, P. Wang, P.-P. Cui, K.Chen, W.-Y. Sun, J. Coord. Chem. 67 (2014) 3854.
[37] Y. Deng, P. Wang, Y. Zhao, Y.-S. Kang, W.-Y. Sun, Micropor. Mesopor, Mater. 227
(2016) 39.
[38] A. Dutta, A.G. Wong-Foya, A.J. Matzger, Chem. Sci. 5 (2014) 3729.
[39] Y. Liu, Y. Chen, T. Liu, A.A. Yakovenko, A.M. Raiff, H. Zhou, CrystEngComm 15
(2013) 9688.
[40] Y. Wang, W. Fan, X. Wang, D. Liu, Z. Huang, F. Dai, J. Gao, Polyhedron 155 (2018)
261.
[41] J. Fan, B.E. Hanson, Chem. Commun. (2005) 2327.
19

[42] J.K. Kallitsisa, M. Rehahn, G. Wegner, Makromol. Chem. 193 (1992) I021.
[43] Apex2, Data Collection Program for the CCD Area-Detector System; SAINT, Data
Reduction and Frame Integration Program for the CCD Area-Detector System. Bruker
Analytical X-ray Systems, Madison, Wisconsin, USA, 1997-2006.
[44] SAINT, data reduction and frame integration program for the CCD area-detector system;
Bruker Analytical X-ray Systems: Madison, WI, 2006.
[45] G. Sheldrick, Program SADABS: Area-detector absorption correction, University of
Göttingen, Germany, 1996.
[46] CrysAlis RED. O.D.L. Version 1.171.34.76.2003.
[47] a) A.L. Spek, Acta Crystallogr. D65 (2009) 148; (b) A.L. Spek. J. Appl. Crystallogr. 36
(2003) 7; (c) A. L. Speck, PLATON - A Multipurpose Crystallographic Tool, Utrecht
University, Utrecht, The Netherlands, 2008; Windows implementation: L.J. Farrugia,
University of Glasgow, Scotland, Version 40608 (2008).
[48] G.M. Sheldrick, Acta Crystallogr. A64 (2008) 112.
[49] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds.
Part A: Theory and Applications in Inorganic Chemistry; Part B: Application in
Coordination, Organometallic, and Bioinorganic Chemistry, fifth ed., Wiley, New York,
1997.
[50] A.W. Addison, T.N. Rao, J. Reedijk, J. van Rijn, G.C. Verschoor, J. Chem. Soc., Dalton
Trans. (1984) 1349.
[51] (a) S. Millan, B. Gil-Hernández, E. Milles, S. Gökpinar, G. Makhloufi, A. Schmitz, C.
Schlüsener, C. Janiak, Dalton Trans. 48 (2019) 8057. (b) S. Glomb, D. Woschko, G.
Makhloufi, C. Janiak, ACS Appl. Mater. Interfaces. 9 (2017) 37419.
[52] J.F. Eubank, L. Wojtas, M.R. Hight, T. Bousquet, V.C. Kravtsov, M. Eddaoudi, J. Am.
Chem. Soc. 133 (2011) 17532.
[53] E.V. Pakhmutova, A.E. Malkov, T.B. Mikhailova, A.A. Sidorov, I.G. Fomina, G.G.
Aleksandrov, V.M. Novotortsev, V.N. Ikorskii, I.L. Eremenko, Izv. Akad. Nauk SSSR,
Ser. Khim.(Russ.), Russ. Chem. Bull. 52 (2003) 2117.
[54] R.J. Pakula, J.F. Berry, Dalton Trans. 47 (2018) 13887.
[55] J. Cui, W. Zhang, Synth. React. Inorg., Met.-Org., Nano-Met. Chem. 44 (2014) 1154.
Vasile Lozan: Conceptualization, Methodology, Investigation, Writing - Review & Editing,
Supervision. Gamall Makhloufi: Data curation. Vadim Druta: Methodology, Investigation,
Writing - Original Draft. Paulina Bourosh: Formal analysis, Writing - Original Draft.
Victor Ch. Kravtsov: Formal analysis. Narcisa Marangoci: Data curation. Christian
Heering: Data curation. Christoph Janiak: Conceptualization, Writing - Review & Editing
20

Declaration of interests
☒ The authors declare that they have no known competing financial interests or personal
relationships that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be
considered as potential competing interests:
The elongated linker 2',3',5',6'-tetramethylterphenyl-4,4''-dicarboxylic acid
(H2L) was employed in the synthesis of zinc(II) and cobalt(II) coordination polymers with
single or mixed bridging ligands. Seven compounds, that include the solvate H2L·2DMSO
(1·2DMSO), the 1D coordination polymer [Zn(L)(DMF)2]n (2), the two 2D coordination
polymers {[Zn(L)(DEF)]2·2DEF}n (3) and {[Co(L)(DEF)]2·2DEF}n (4), and the three mixed
ligand 3D coordination polymers {[Zn2(L)2(BIBP)]·2DEF}n (5), {[Co2(L)2(BIBP)]·2DEF}n
(6) and {[Zn3(L)3(BIPY)1.5]·4DMF·1.5H2O}n (7), (where DMSO is dimethylsulfoxide, DMF
is dimethylformamide, DEF is diethylformamide, BIBP stands for 4,4′-bis(1-
imidazolyl)biphenyl, and BIPY for 4,4'-bipyridine) have been synthesized and characterized
by IR spectroscopy, thermogravimetry, and single-crystal X-ray diffraction. In 2 the zinc atom
adopts a tetrahedral O4 environment due to the monodentate coordination of two DMF
molecules and two deprotonated bridging L2- ligands. The latter connect the zinc atoms in a
zigzag-like chain. In the coordination polymers 3 to 7 the secondary building unit (SBU) is
the paddle-wheel moiety {M2(O2C-)4(N/O)2}. The metal atoms are five coordinated with
21

distorted square pyramidal coordination geometry by oxygen atoms from carboxylate groups
of four different L2- linkers, and one axial DEF-O atom in 3 and 4, BIBP-imidazolyl-N atom
in 5 and 6 or BIPY-N atom in 7. Furthermore, the L2- ligands link the SBUs to a (4,4) 2D sql
net. In 5-7 these sql nets are additionally linked by BIBP or BIPY ligands as pillars to provide
pillared-layer 3D and three-fold interpenetrated frameworks. Remarkably, the BIBP pillar
yields bsn (beta-Sn) topology, the BIPY pillar pcu (-Po) topology.
22