Coordination polymers incorporating Bi(III) and 2,4,6-pyridine tricarboxylic acid and its derivatives: Synthesis, structure and topology

Article abstract of DOI:10.1016/j.poly.2020.114564

Bi(III) as its oxide combined with 2,4,6-pyridine tricarboxylic acid, H₂pdc-COOH, and various pyridine-derived additives in dimethylformamide (dmf) under solvothermal conditions produced three novel bismuth coordination polymers, {[Bi(μ-pdc-COO)₂][NH₂Me₂]₃}_n, 1, {[Bi(μ-pdc-COO)₂][C₅H₇N₂]₃·C₅H₆N₂}_n, 2, and {[Bi₂(μ-pdc-COO)₂(μ-pdc-COOH)(pdc-COOH)][NH₂Me₂]₄·2dmf·NHMe₂}_n, 3. The anionic coordination network topologies are two-dimensional, chains-of-loops and ladders, respectively, but the local 8-coordinate environments about the bismuth(III) centres are in each case between that of a square antiprism and that of a hexagonal bipyramid. When the 4-carboxy substituent in H₂pdc-COOH is replaced by another potentially coordinating substituent to give 4-R-2,6-pyridine dicarboxylic acid, H₂pdc-R (R = OH, NH₂, Cl), the salts obtained contain discrete centrosymmetric dinuclear 8-coordinate bismuth anions with either double O-bridges between the metal centres, [Bi₂(μ-pdc-R)₂(pdc-R)₂(dmf)₂][NH₂Me₂]₂ (R = OH, NH₂), 4 and 5, or double carboxylate bridges with one long Bi–O bond, [Bi₂(μ-pdc-NMe₂)₂(pdc-NMe₂)₂(dmf)₂][NH₂Me₂]₂, 6 (R = Cl, but replaced by dimethylamine during the reaction). The structures and supramolecular networks of 1–6 are described and compared as an exploration of alternatives to the conventional carboxylate-based organic linking units.

Full text of DOI:10.1016/j.poly.2020.114564

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Coordination polymers incorporating Bi(III) and 2,4,6-pyridine tricarboxylic
acid and its derivatives: synthesis, structure and topology
Levi Senior, Anthony Linden
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S0277-5387(20)30221-7
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POLY 114564
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14 April 2020
Please cite this article as: L. Senior, A. Linden, Coordination polymers incorporating Bi(III) and 2,4,6-pyridine
tricarboxylic acid and its derivatives: synthesis, structure and topology, Polyhedron (2020), doi: https://doi.org/
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Coordination polymers incorporating Bi(III) and 2,4,6-pyridine
tricarboxylic acid and its derivatives: synthesis, structure and topology
Levi Senior, Anthony Linden*
Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
Abstract
Bi(III) as its oxide combined with 2,4,6-pyridine tricarboxylic acid, H2pdc-COOH, and various
pyridine-derived additives in dimethylformamide (dmf) under solvothermal conditions produced three
novel bismuth coordination polymers, {[Bi(-pdc-COO)2][NH2Me2]3}n, 1, {[Bi(-pdc-
COO)2][C5H7N2]3·C5H6N2}n, 2, and {[Bi2(-pdc-COO)2(-pdc-COOH)(pdc-
COOH)][NH2Me2]4·2dmf·NHMe2}n, 3. The anionic coordination network topologies are two-
dimensional chains-of-loops and ladders, respectively, but the local 8-coordinate environments about
the bismuth(III) centres are in each case between that of a square antiprism and that of a hexagonal
bipyramid. When the 4-carboxy substituent in H2pdc-COOH is replaced by another potentially
coordinating substituent to give 4-R-2,6-pyridine dicarboxylic acid, H2pdc-R (R = OH, NH2, Cl), the
salts obtained contain discrete centrosymmetric dinuclear 8-coordinate bismuth anions with either
double O-bridges between the metal centres, [Bi2(-pdc-R)2(pdc-R)2(dmf)2][NH2Me2]2 (R = OH,
NH2), 4 and 5, or double carboxylate bridges with one long Bi–O bond, [Bi2(-pdc-NMe2)2(pdc-
R)2(dmf)2][NH2Me2]2, 6 (R = Cl, but replaced by dimethylamine during the reaction). The structures
and supramolecular networks of 1-6 are described and compared as an exploration of alternatives to
the conventional carboxylate-based organic linking units.
Keywords: Bismuth; 2,4,6-pyridine tricarboxylic acid; 2,6-pyridine dicarboxylic acid;
Framework; MOF; structural characterization
1

1. Introduction
Reticular chemistry entails a ‘building block’ approach to developing porous compounds that
extend infinitely in 1-3 dimensions [1]. Primarily explored using transition metal elements, such
compounds have been researched extensively over the past two decades [2]. Although many potential
applications have been touted over the lifetime of this field, research tends to be geared towards
developing porous materials as tools for gas sorption, separation and catalysis; their capacity as a
drug-delivery system receives less attention [3].
Bismuth is a non-toxic metal element of some medicinal value [4] – currently used to treat
gastrointestinal problems. A small range of bismuth-based metal-organic framework (MOF) materials
have been developed through the employment of the same carboxylate-based linkers frequently used
in the synthesis of d-block MOFs [5]. Few instances of polymeric bismuth complexes utilising non-
carboxylate organic linking ligands have been reported to date [6-9].
We are exploring the chemistry of extended bismuth structures by employing the tridentate
2,4,6-pyridine tricarboxylic acid, H2pdc-COOH (Fig. 1), derivatives of which have been shown to be
biodegradable in bacterial samples [10], in an attempt to find a stable structural building unit from
which to construct multidimensional frameworks in a consistent and predictable manner. In this work,
H2pdc-COOH was employed alongside bismuth(III) oxide, Bi2O3, dmf and aminopyridine additives in
solvothermal syntheses in order to synthesize a series of novel extended bismuth structures. Other 4-
R-2,6-pyridine dicarboxylic acids, H2pdc-R, in which the 4-carboxylic acid group of H2pdc-COOH is
replaced by another group (R = OH, NH2, Cl), were also employed, but led only to dinuclear Bi(III)
complexes. The resulting structures vary in overall topology and dimension, while possessing
analogous connectivity around the bismuth cation.
Fig. 1. The organic acids H2pdc-COOH (left) and H2pdc-R (right; R = OH, NH2, Cl).
2. Experimental
2.1. Materials and methods
Bi(NO3)3.5H2O (97%) and Bi2O3 were purchased from Sigma-Aldrich; Chelidamic acid
monohydrate (95%) and 4-chloro-2,6-pyridine dicarboxylic acid were purchased from TCI
Deutschland GmbH. All chemicals were commercially available and used without further
purification. 1H and 13C NMR spectra were recorded on a Bruker Ascend 400 MHz NMR
2

spectrometer. Solubility limitations precluded the recording of NMR spectra of the bismuth
complexes.
2.1.1. Synthesis of 2,4,6-pyridine tricarboxylic acid (H2pdc-COOH)
H2pdc-COOH was synthesized according to the literature [11]. To 2,4,6-trimethylpyridine
(4.84g, 0.04 mol) in H2O (80 mL) in a 250 mL round-bottomed flask, KMnO4 (50 g, 0.32 mol) was
added over 4 hours while maintaining a temperature of 20-30°C. The resulting mixture was left to stir
at room temperature for 16 hours. Increasing the temperature to 50°C, the reaction mixture was left to
stir for a further 48 hours before cooling and filtering through fritted filter paper in order to remove
solid MnO2 from the reaction. The residue was washed with distilled water and the resulting filtrate
evaporated to yield a white solid (3.24g, 38%). 1H NMR (400 MHz, D2O): 훿 8.58 (s, 2H). 13C NMR
(400 MHz, D2O): 훿C 127.4, 142.2, 148.5, 166.5, 166.9.
2.1.2. Synthesis of 4-amino-2,6-pyridine dicarboxylic acid (H2pdc-NH2)
H2pdc-NH2 was synthesized according to the literature [18].
2.2. Preparation of Bi(III) complexes 1-6
2.2.1. {[Bi(-pdc-COO)2][NH2Me2]3}n (1)
H2pdc-COOH (50 mg, 0.2368 mmol) was dissolved in dimethylformamide (dmf, 6 mL) in a
15 mL screw-capped vial. Bi2O3 (110.3mg, 0.2368 mmol) was added, the cap screwed on tightly and
the vial sonicated at room temperature for 10 minutes. The yellow suspension was heated at 120°C for
24 h before cooling in the oven to room temperature. Crystals of 1 were harvested by hand from atop
a layer of grey-black crystalline powder.
2.2.2. {[Bi(-pdc-COO)2][C5H7N2]3·C5H6N2}n (2)
H2pdc-COOH (50 mg, 0.2368 mmol) was dissolved in dmf (6 mL) in a 15 mL screw-capped
vial. Bi2O3 (110.3 mg, 0.2368 mmol) and 4-aminopyridine (22.29 mg, 0.2368 mmol) were added and
the vial sonicated at room temperature for 10 minutes. The vial was transferred to an oven and heated
at 120°C for 24 h before cooling in the oven to room temperature. A layer of colourless needle-like
crystals 2 could be observed atop a mass of green-black material; crystals were harvested by hand
from the reaction mixture.
2.2.3. {[Bi2(-pdc-COO)2(-pdc-COOH)(pdc-COOH)][NH2Me2]4·2dmf·NHMe2}n (3)
H2pdc-COOH (50 mg, 0.2368 mmol) was dissolved in dmf (6 mL) in a 15 mL screw-capped
vial. Bi2O3 (110.3 mg, 0.2368 mmol) and either 3-aminopyridine, 2-aminopyridine, or 4,4’-bipyridine
3

(0.2368 mmol) were added and the vial sonicated at room temperature for 10 minutes. The vial was
transferred to an oven and heated at 120°C for 24 h before cooling in the oven to room temperature. A
layer of colourless needle-like crystals 3 could be observed atop a mass of green-black material;
crystals were harvested by hand from the reaction mixture.
2.2.4. [Bi2(-pdc-R)2(pdc-R)2(dmf)2][NH2Me2]2 [R = OH (4), NH2 (5)]
H2pdc-OH or H2pdc-NH2 (50 mg) was dissolved in dmf (6 mL) in a 15 mL screw-capped
vial. Bi2O3 (1 equiv.) was added and the vial sonicated at room temperature for 10 minutes. The vial
was transferred to an oven and heated at 120°C for 24 h before cooling in the oven to room
temperature. Colourless block-shaped crystals were harvested by hand from the reaction mixture.
2.2.5. [Bi2(-pdc-NMe2)2(pdc-R)2(dmf)2][NH2Me2]2 (6)
H2pdc-Cl (50 mg) was dissolved in dmf (6 mL) in a 15 mL screw-capped vial. Bi2O3 (1
equiv.) was added and the vial sonicated at room temperature for 10 minutes. The vial was transferred
to an oven and heated at 120°C for 24 h before cooling in the oven to room temperature. Colourless
block-shaped crystals of 6 were harvested by hand from the reaction mixture.
2.3. X-ray Crystallography
Single-crystal data for 1-6 were collected on a Rigaku Oxford Diffraction SuperNova area-
detector diffractometer [13] using Mo K radiation ( = 0.71073 Å) from a micro-focus X-ray source
and an Oxford Instruments Cryojet XL cooler set to 160 K. Data reduction was performed with
CrysAlisPro [13]. Structure solutions were carried out using the SHELXT-2018 [14] program,
followed by refinement using SHELXL-2018 [15]. The crystallographic data are listed in Table 1.
The dimethylammonium cations in 1 are disordered: two sets of positions were defined for
each cation, with the site occupancy of the major component refining to 0.707(10) for the cation in the
general position and being 0.5 by definition for the cation disordered about the two-fold axis.
Similarity restraints were applied to all C–N bond lengths in the cations, while neighbouring atoms
within and between each orientation of the disordered cations were restrained to have similar atomic
displacement parameters (ADPs). Although none of the species in compound 1 has a stereogenic
centre, it has crystallized in a chiral space group and the absolute structure parameter, determined by
the method of Parsons et al. [16] using 1559 quotients, was -0.030(4). For 2, the 4-aminopyridinium
cation site shared with a neutral 4-aminopyridine molecule is disordered (see Section 3.2.2). The site
occupation factor of the major orientation of the disordered cation refined to 0.779(17). Similarity
restraints akin to those used for 1 were applied and, in addition, the disordered orientations were
restrained to be planar. For 3, there is complete disorder of the two tridentate ligands coordinating to
4

Bi2. Two sets of positions were defined for these ligands and the site occupation factor of the major
conformation refined to 0.540(6). Similarity restraints were applied to the chemically equivalent bond
lengths and angles, as well as the ADPs, involving all disordered atoms and each ligand was also
restrained to be planar. The SQUEEZE procedure of the program PLATON [17] was applied; see
Section 3.2.3. For 4 and 6, the dmf ligand is disordered and the site occupation factor of the major
conformation refined to 0.60(2) and 0.577(8), respectively. Similarity restraints, analogous to those
described for 1, were applied.
H-atoms were generally placed in calculated positions and allowed to ride on their parent
atoms. The exceptions were the hydroxy H-atoms in 4, the ligand amine H-atoms in 5 and the
ammonium H-atoms in 6, all of which were refined isotropically.
Table 1
Crystallographic data for 1–6.
3. Results and discussion
3.1. Syntheses
Compound 1 resulted from the solvothermal reaction between Bi2O3 and H2pdc-COOH alone
in dmf. The reactions that included various pyridines as additives were conducted to evaluate the role
of the pKa of the pyridine in structure direction. While compound 2 resulted from the use of 4-
aminopyridine (pKa = 9.17), compound 3 was obtained consistently with 3-aminopyridine (pKa =
6.00), 2-aminopyridine (pKa = 6.86), or 4,4’-bipyridine (pKa = 10.73). The results from this limited
selection of pyridines suggest that pKa is not a sole or major contributor. The differences observed
between the three products 1-3 could be related to the rate of the reaction. For 1, H2pdc-COOH is
slowly deprotonated by the oxidization of dmf to dimethylamine or dimethylammonium cations [18].
In 2 and 3, however, the H2pdc-COOH at the start of the reaction will already be in a somewhat
deprotonated state as a consequence of the added pyridine derivative: an increased rate of
coordination ensues, potentially influencing the arrangement of the developing framework. In 2, the
positioning of the H-donor/acceptor groups (1,4-position) of the base are such that extended chains
are effectively tied together. Dimethylamine or dimethyl ammonium cations are not found in the
crystals of 2, possibly because the more stable crystal lattice in terms of packing and hydrogen
bonding arises when 4-aminopyridinium is incorporated.
The solvothermal syntheses of compounds 1-6 resulted in crystals of the reported compounds
being isolated by hand from a further mass of material left after the reaction. X-ray powder diffraction
of the bulk material indicated that it was predominantly unreacted Bi2O3, which dominated the
5

background of the diffractograms and prevented their meaningful analysis. Attempts to isolate
sufficient crystals by hand did not give enough material to obtain a clean diffractogram.
As Bi2O3 is only very slightly soluble in dmf, a clean stoichiometric reaction is considered
unlikely. Reactions were attempted with various ligand:bismuth ratios (0.5:1, 1:1, 1:2, 1:3 and vice
versa), along with different solvent quantities (3, 5, 6 and 8 mL) and temperatures (95, 120, 150 °C).
None of these modifications made any significant difference to the reaction outcomes. The best
crystals generally came from the 1:1 molar ratio of ligand:bismuth; crystals of 3 were very delicate
when touched. A further advantage of using dmf as the solvent was that it avoided having water
competing as a bismuth-coordinating ligand.
3.2. Bi(III) coordination polymers
3.2.1. {[Bi(-pdc-COO)2][NH2Me2]3}n (1)
Reaction of H2pdc-COOH with Bi2O3 (1:1) in dmf at 120°C yielded phase-pure colourless
block crystals of 1 within 24 hours. Single crystal analysis of 1 revealed a 2-dimensional anionic
framework with overall stoichiometry {[Bi(-pdc-COO)2][NH2Me2]3}n, space group I2.
The asymmetric unit of 1 contains one fully deprotonated pdc-COO ligand, one half of a
bismuth(III) cation (sits on a two-fold axis) and 1.5 dimethylammonium cations (one cation site is
disordered about a two-fold axis and the other site is disordered in a general position). Expanding the
structure reveals that each bismuth cation is 8-coordinated by two tridentate pdc-COO moieties and
monodentate oxygen atoms from the 4-carboxy group of two further pdc-COO ligands (Fig. 2). The
tridentate pdc-COO ligands lie in planes inclined to one another by 84.16(16)° and monodentate
binding sites subtend an angle of 103.78(18)° at the Bi(III) centre. Interestingly, the Bi–O bond
lengths in the chelated rings are unequal (Table 2). The 8-coordinate local topology is discussed
further in Section 3.2.4.
Fig. 2. Displacement ellipsoid plot of the Bi(III) coordination environment in 1 (50% probability ellipsoids;
symmetry codes: (i) -3/2-x, ½+y, -3/2-z; (ii) ½+x, ½+y, ½+z; (iii) -1-x, y, -1-z).
Table 2
Symmetry-unique bond distances (Å) around the central bismuth(III) centre in 1 and 2.
Each pdc-COO ligand bridges two Bi(III) cations and each Bi(III) is coordinated by four
linkers to give extended 2-dimensional anionic sheets based on an oblique 9.62  6.62 Å grid having a
(4,4) net by Wells notation [19] (Fig. 3). The point symbol for the net, calculated using ToposPro
[20], is {84.122}{8}2, a 2-nodal 2,4 net with stoichiometry (2-c)2(4-c), and apparently a new topology
6

101
(Fig. S1). The sheets lie parallel to the (
) plane and the acute oblique angle defining the grid shape
is 51.75(1)°. The shortest Bi···Bi distance across one grid unit is 8.3985(3) Å. Dimethylammonium
cations sit in the spaces between the sheets, aligned roughly above the parallelepiped pores. In the
crystal structure, the sheets stack slightly slipped relative to their normals, with the Bi(III) ions in
successive sheets stacked along the [100] direction at a distance of 10.1017(2)Å. Nonetheless, open
channels exist through the pores of the stacked sheets. Although there are no solvent accessible voids
in the overall structure according to void space calculations run through PLATON [17], removing the
dimethylammonium cations results in void spaces within the anionic lattice of 583 Å3 per unit cell
(42% of the unit cell volume). Much of this space lies between the anionic layers, rather than within
the grids of the layers. Interionic N–H···O hydrogen bonds between the cations and carboxylate O-
atoms complete the three-dimensional supramolecular framework (Table 3).
Fig. 3. The square channels in 1 (left; viewed down the c-axis) formed by the layering of 2-dimensional sheets
(right; viewed down the b-axis). Cation disorder not shown.
Table 3
Hydrogen-bond parameters for 1–6.
3.2.2. {[Bi(-pdc-COO)2][C5H7N2]3·C5H6N2}n (2)
With the addition of 1 molar equivalent of 4-aminopyridine to the reaction setup that
produced 1, crystals of 2 were obtained as colourless needles.
Single crystal analysis of 2 revealed a space group of I2/a. The Bi(III) cation in {[Bi(-pdc-
COO)2][C5H7N2]3·C5H6N2}n lies on a two-fold axis and the asymmetric unit additionally includes one
pdc-COO anion, one ordered 4-aminopyridinium cation and one disordered site occupied 50% by
another 4-aminopyridinium cation and 50% by a neutral 4-aminopyridine molecule. The distinction
between cation and neutral species at the disordered site in the structure model is unclear, but a
required assumption for charge balance. Bismuth has a very similar 8-coordinate geometry to that
observed in 1 (Fig. 4), but here the Bi–O distances in the chelating linkage are a more equivalent than
in 1 (Table 2). Topological differences to that observed in 1 do, however, present themselves in the
alignment of the pdc-COO ligands in 2 (Fig. 5): instead of adjacent tridentate and monodentate
ligands at the same Bi(III) centre running off approximately at right angles to form two sides of the
oblique grid, the same two ligands have twisted about their 4-carboxylate groups so that opposite ends
bond to the same adjacent Bi(III) cation. These two ligands are then related across a centre of
inversion and form a double pdc-COO bridge between adjacent Bi(III) centres which lie 8.6122(2) Å
apart. The consequence of this is that the extended structure of 2 exists as one-dimensional ribbon-like
chains directed along the [100] direction. A (2,4) net results according to Wells notation. The circuit
7

enclosed by one chain link measures approximately 8.61  3.27 Å. Each chain runs along a
crystallographic two-fold axis and all chains in the structure are parallel with the shortest interchain
Bi···Bi distances being 10.5547 (5) and 11.5660(9) Å. The 4-aminopyridinium cations and 4-
aminopyridine solvent molecules are distributed within the channels that run parallel to the anionic
chains. Void space calculations run through PLATON show that 59% of the unit cell volume (2125
Å3) is void upon removal of the cations and solvent molecules.
Fig. 4. Displacement ellipsoid plot of the Bi(III) coordination environment in 2 (50% probability ellipsoids;
symmetry codes: (i) 1-x, 1-y, 1-z; (ii) ½+x, 1-y, z; (iii) 3/2-x, y, 1-z).
Each ordered 4-aminopyridinium cation cross-links three anionic chains of 2 through N–
H···O hydrogen-bonds (Table 3) between all available N–H donors and adjacent pdc-COO
carboxylate O-atoms (two coordinating and one non-coordinating O-atom). Pairs of 4-aminopyridine
cations sit either side of centres of inversion with their amine groups facing inwards, thereby forming
R4(12)
a
graph set motif [21] with the carboxylate O-atoms from two chains. The disordered cations
4
also congregate in pairs across centres of inversion and each of these cations cross-links two anionic
chains. Overall, the classic hydrogen-bonding interactions complete a three-dimensional framework
of cations and anionic chains (Fig. 5). There are π···π interactions between the parallel pyridine rings
within each centrosymmetric double pdc-COO bridge (see Table 4 for the parameters). Short
centrosymmetric stacks of four 4-aminopyridinium cations also show π···π interactions; the inner pair
have significant slippage of their centres of gravity, while the outer pair are aligned with little
slippage, but the ring planes are tilted by 12.8(7)°.
Fig. 5. Graphical representation of 2: 1-dimensional ribbons are interconnected through a hydrogen-bonding
network. Cation disorder not shown.
Table 4
Geometric parameters of the π···π interactions in 2–6.
3.2.3. {[Bi2(-pdc-COO)2(-pdc-COOH)(pdc-COOH)][NH2Me2]4·2dmf·NHMe2}n (3)
Replacing 4-aminopyridine, as used to produce 2, with either of 2-aminopyridine, 3-
aminopyridine or 4,4’-bipyridine yielded colourless needles of 3 in each instance. Single crystal
analysis revealed a space group of I2/a.
The model for the asymmetric unit of 3 contains two symmetry-independent Bi(III) cations
two pdc-COO and two monoprotonated pdc-COOH anions, two dimethylammonium cations and a
dmf molecule. The carboxylic acid group at the 4-position of the pyridine ring of the pdc-COOH
ligand coordinated to Bi1 is non-coordinating and the H-atom could be located. The C–O distances in
8

this group also support the presence of carboxylic acid and not carboxylate. The corresponding H-
atom of the pdc-COOH ligand could not be located, because of complete disorder of the tridentate
ligands coordinating to Bi2, but is assumed to be there; that carboxylic acid group is also non-
coordinating. The C–O distances are less indicative in this case, because of restraints used for the
disorder modelling. No additional species were unambiguously discernible in difference electron
density maps, but four void spaces of 682 Å3 remain per unit cell, which equates to 341 Å3 per
asymmetric unit. Application of the SQUEEZE procedure [17] revealed 119 e per asymmetric unit.
Given that the species described above leave a charge imbalance, it is assumed that there are two
more dimethylammonium cations in the void space in the asymmetric unit and the void-space electron
count is matched if one assumes one additional dimethylamine molecule and one additional dmf
molecule are also in the asymmetric unit. Thus the overall composition of 3 is proposed as being
{[Bi2(-pdc-COO)2(-pdc-COOH)(pdc-COOH)][NH2Me2]4·2dmf·NHMe2}n.
The two symmetry-independent Bi(III) centres each have similar atomic connectivity to that
observed in each of 1 and 2: bismuth is 8-coordinated by two tridentate pdc-COO ligands, one of
which is pdc-COOH, and two monodentate carboxylate oxygen atoms from two further pdc-COO
ligands (Fig. 6). However, the origins of the monodentate oxygen atoms differ for each Bi centre. At
Bi1, the monodentate interactions are with an oxygen atom of the 4-carboxy-position of two different
pdc-COO ligands. At Bi2, one monodentate interaction is with the second oxygen atom of the 4-
carboxy-position of one of the monodentate pdc-COO ligands interacting with Bi1, so that this
carboxylate group is ditopic and links Bi1 to Bi2, while the other monodentate interaction is with one
of the ortho-carboxylate groups of the pdc-COOH ligand of Bi1 thereby forming an additional O-
atom bridge between Bi1 and Bi2. This connectivity results in a highly distorted 6-membered Bi2CO3
ring; a motif that is not present in the structures of 1 and 2. The Bi–O and Bi–N bond distances (Table
5) are in similar ranges to those found in structures 1 and 2, with a slightly wider variation because the
Bi–O distances involving oxygen atoms involved in the bridges within the Bi2CO3 ring tend to be
slightly longer than otherwise.
Fig. 6. Displacement ellipsoid plot of the Bi(III) coordination environment in 3 (50% probability ellipsoids;
major disorder conformation; symmetry codes: (i) x, 1+y, z; (ii) x, -1+y, z).
Table 5
Bond distances (Å) around each of the two bismuth(III) environments in 3a.
The supramolecular anionic structure is that of ladders extending in the [010] direction (Fig.
6). The uprights in the ladder are composed solely of Bi1 centres on one side and Bi2 centres on the
other side, with adjacent Bi-centres along each upright being linked by a single pdc-COO ligand
9

through its head and tail. The rungs of the ladder are formed by the cross-linking effect of the Bi2CO3
ring. The pdc-COOH ligands act as decoration protruding from the ladder as terminal extensions of
the rungs. The Wells notation for the ladder motif is (4,3). The Bi···Bi distance across the ladder rung
is 4.4630(16) Å, while the Bi···Bi distance along each upright is 9.5592(6) Å. The resultant pore
between the roughly antiparallel pdc-COO ligands in the rungs of the ladder is extremely distorted.
It is difficult to be definitive about the dimensionality of the supramolecular network
generated by the hydrogen-bonding interactions, because not all cations and solvent molecules could
be included in the model. The two defined dimethylammonium cations reinforce the ladder motif
through their hydrogen bonds (Table 3). The carboxylic acid group of one pdc-COOH ligand cross-
links adjacent ladders via the free oxygen atom of a carboxy group involved in the tridentate
coordination to a bismuth cation to give a two-dimensional network of sheets that lies parallel to the
(001) plane. Although the H-atom of the other pdc-COOH ligand could not be located, the O···O
distances suggest there is an interaction here which links two adjacent sheets related by a centre of
inversion into pairs. These double sheets then stack along [001] with dimethylammonium cations and
dmf solvent molecules between them (Fig. 7). There are weak π···π interactions between the N4-
pyridine rings of disordered non-bridging pdc-COOH ligand in adjacent ladders, so that these pendant
ligands interdigitate (Table 4). The other pdc-COOH ligand and the pdc-COO ligand are not involved
in such interactions.
Fig. 7. The extended chains in 3 sandwiching a channel of hydrogen-bonded dimethylammonium counterions
and dmf molecules (the minor component of the anion disorder and the upper part of the unit cell box are not
shown).
3.2.4. Comparison of the structures of the Bi(III) coordination polymers
Each of the structures 1-3 possesses the same bis-tridentate Bi(pdc-COO)2 core, with a
dihedral angle between the pdc-COO planes of approximately 85-90°. The Bi(III) centres are always
8-coordinate with the two remaining bonding interactions arising from either the 4-carboxylate group
of adjacent pdc-COO ligands or, as in the case of 3 only, a bridging interaction involving one of the
tridentate-binding carboxylate oxygen atoms. No solvent molecules or non-pdc-COO entities are
bound directly to Bi(III). 1 and 2 are identical in the sense of coordination environment at each
bismuth centre. Differences in topology in this case arise from the relative orientation of the pdc-COO
ligands: in 1, chains of ligands intersect at the Bi(III) centres to give an oblique two-dimensional grid
pattern with sides strictly parallel (Fig. 3). In 2, adjacent Bi(III) centres are linked via a
centrosymmetric double-bridge through two antiparallel pdc-COO moieties to give a chain-of-rings
motif. Each successive link in the chain is approximately orthogonal to its neighbour, giving rise to
the ribbon-like topology. The structure of 3 also contains a comparable sub-structure chain motif to
that found in 1, but additional bridging modes not observed in 1 are present, leading to the anionic
10

ladder structure (Fig. 6).
The local coordination topology of the Bi(III) centres in all structures, including the structures
of 4-6 discussed below, can be analysed in terms of the ideas of Kepert for 8-coordinate bis(tridentate
ligand) bis(monodentate ligand) metal complexes [22]. The angle subtended at the Bi(III) centre for
the formally monodentate connections lie between 95 and 126°. The higher end of this range (116-
126°) is adopted by monodentate connections where at least one of the connections is part of a bridge
between Bi(III) centres, while 103-106° occurs when there are two monodentate non-bridging ligands,
as only found in 1 and 2. An outlier of 95° occurs at Bi2 in 3 where both monodentate ligands are O-
or carboxylate-bridging. All N–Bi–N angles between tridentate ligands are tightly clustered between
125 and 134° across all structures, while the O···N···O angles (the ABC definition of Kepert) range
from 112-116°. The normalized bite of a tridentate ligand, the b-value of Kepert, is defined as the
(mean) distance between the donor atoms of the chelate divided by the (mean) metal-donor atom
distance [22]. The b-values for 1-6 have a very narrow range of 1.04 to 1.09. The values from the
structures reported here are thus consistent with the examples of Kepert, which are attributed to a
coordination topology that lies between that of a square antiprism and that of a hexagonal bipyramid.
3.3. Discrete Bi(III) anionic complexes: substituting the 4–COOH group
The effect on the Bi-coordinating and framework-building properties of pdc-COO was
investigated by replacing the carboxylic acid at the 4-position of the pdc-COO ring with another
potentially coordinating substituent, namely 4-hydroxy, 4-amino and 4-chloro.
3.3.1. [Bi2(-pdc-R)2(pdc-R)2(dmf)2][NH2Me2]2 [R = OH (4), NH2 (5)]
The reaction of Bi2O3 with the 4-hydroxy-2,6-pyridine dicarboxylic acid and 4-amino-2,6-
pyridine dicarboxylic acid derivatives, H2pdc-OH and H2pdc-NH2, under the same conditions used for
the synthesis of 1-3 gave rise to discrete centrosymmetric dinuclear Bi(III) anions as their
dimethylammonium salts, 4 (Fig. 8) and 5 (Fig. S2), respectively. Each of these complexes
1
crystallized as colourless blocks with space group P and their structures are essentially isostructural.
Each has the general formula [Bi2(-pdc-R)2(pdc-R)2(dmf)2][NH2Me2]2, wherein the asymmetric unit
contains a single bismuth centre coordinated by two pdc-R ligands in a tridentate pincer-like manner,
a disordered dmf ligand coordinating via its O-atom and a discrete dimethylammonium counter-ion.
One of the carboxylate O-atoms coordinating to the bismuth centre also coordinates to the other,
centrosymmetrically-related, bismuth centre in the anion. This completes the 8-coodination of each
bismuth centre and the two Bi(III) centres are thus bridged by two O-atoms to give a Bi2O2 core
(Table 6). The pdc-R ligand not involved in the O-bridge and the dmf ligand lie roughly perpendicular
to the Bi2O2 plane. A similar dinuclear anion has been observed in the structure of the 2-amino-3-
11

ammoniopyridinium salt of [Bi2(-pdc)2(pdc)2(H2O)2] [23].
Fig. 8. Displacement ellipsoid plot of the dinuclear Bi(III) anion and Bi2O2 core in 4 (50% probability
ellipsoids; major disorder conformation of the dmf ligand; symmetry code: (i) 1-x, 1-y, 1-z). The anion in 5 is
almost identical in appearance.
Table 6
Bond distances (Å) around the unique bismuth(III) centre in 4-6.
In 4, N–H···O hydrogen bonds from pairs of dimethyl ammonium cations link adjacent
011
anions into a supramolecular chain, which runs parallel to the [
] direction. The hydrogen-bond
acceptors are non-coordinating carboxylate O-atoms of pdc-OH ligands (Table 3). The hydroxy group
of one symmetry-independent pdc-OH ligand forms a hydrogen bond with a non-coordinating
carboxylate O-atom of an anion from a different supramolecular chain, while the other hydroxy group
interacts with a coordinating carboxylate O-atom of an anion in a third chain. Taken together, the
hydrogen-bonding interactions link all species in the crystal into a three-dimensional supramolecular
framework, which consists of alternating layers of cations and anions lying parallel to (001) (Fig. 9).
The pattern of hydrogen bonding interactions in 5 is very similar (Fig. S3), except that one of the
unique amine groups hydrogen-bonds to non-coordinating O-atoms of two other anions from separate
supramolecular chains, while the other amine group hydrogen-bonds to two coordinating O-atoms of
a single neighbouring anion of a fourth chain.
There are weak π···π interactions between centrosymmetrically-related bridging pdc-OH
ligands in adjacent dinuclear anions of 4, which link the anions into stepped chains running parallel to
the [100] direction (Table 4). There are additional weak π···π interactions between
centrosymmetrically-related but quite offset pyridine rings of non-bridging pdc-OH ligands, so that
these pendant ligands from adjacent chains of anions in the [010] direction interdigitate and form
stack of molecules through these rings. Despite the long distances between the centres of gravity of
the rings and the slippage values, it has been argued that such interactions are still energetically
relevant [24]. The π···π interactions in 5 are similar, but the ring slippages and  angles (Table 4)
indicate an even greater offset as a consequence of the spatial influence of the amine group of the pdc-
NH2 ligands.
Fig. 9. Alternating layers of hydrogen-bonded cations and anions in 4 (major disorder conformation of the dmf
ligand; 5 is almost identical).
3.3.2. [Bi2(-pdc)2(pdc-NMe2)2(dmf)2][NH2Me2]2 (6)
Although the reaction between Bi2O3 and H2pdc-Cl was carried out under the same conditions
12

that were used for the synthesis of 4 and 5, the carboxylate ligand (pdc-Cl) undergoes substitution
with dimethylamine derived from the dmf solvent to form pdc-NMe2. Crystallising in space group P
as a colourless plate, the product of the reaction is a crystalline salt, which can be formulated as
1
[Bi2(-pdc)2(pdc-NMe2)2(dmf)2][NH2Me2]2, 6. The anion is a centrosymmetric dinuclear species with
the same distribution of ligands to those in 4 and 5, but it does not contain the Bi2O2 bridge. Instead,
the two Bi(III) centres are loosely joined via a carboxylate bridge, in which one of the Bi–O bonds is
quite long at 2.9689(17) Å (Fig. 10, Table 6). The altered arrangement possibly results from the
presence and exchange of chloride anions in the reaction mixture; dimethylamine has larger spatial
requirements and lacks the hydrogen-bonding capacity exhibited by the 4-substituents associated with
4 and 5.
The discrete dimethylammonium cations form hydrogen bonds with carboxylate O-atoms in
adjacent anions of 6 and thereby link the anions in an alternating fashion into extended chains, which
C2(8)
run parallel to the [010] direction and can be described by a graph set motif of
(Fig. 11, Table
2
3). There are weak very offset π···π interactions between the pdc-NMe2 ligands containing atom N2,
which are involved in the bridging between the Bi(III) centres (Table 4). Each of these pdc pyridine
rings has a further weak centrosymmetric π···π interaction on the other side with its symmetry-related
counterpart from a neighbouring anion and so the anions are linked into slanted stacks, which run
parallel to the [100] direction. Additionally, adjacent stacks in the [010] direction are linked by weak
centrosymmetric offset π···π interactions between the non-bridging pdc-NMe2 ligands containing
atom N1.
Fig. 10. Displacement ellipsoid plot of the dinuclear Bi(III) anion in 6 (50% probability ellipsoids; symmetry
code: (i) 1-x, 1-y, -z).
Fig. 11. The hydrogen-bonded chains of cations and anions in 6.
4. Conclusion
Bismuth coordination polymers were obtained in each case where the pdc-COO ligand was
used, but not when the 4-carboxylate group of the ligand was replaced by the less strongly
coordinating 4-hydroxy, 4-amino and 4-chloro substituents. The underlying net topology of the
bismuth coordination polymers can be altered through varying reaction additives without altering the
local connectivity. Additionally, the use of bismuth oxide as a metal source yields Bi2O2 metal
clusters which provide a promising lead in the further development of extended bismuth-organic
structures.
13

CRediT authorship contribution statement
Levi Senior: Conceptualisation, Investigation, Methodology, Visualisation, Validation, Writing -
original draft. Anthony Linden: Conceptualisation, Supervision, Visualization, Validation, Writing -
review & editing, Project administration.
Declaration of Competing Interest
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.
Acknowledgements
This work was supported by the Department of Chemistry, University of Zurich, Switzerland.
Appendix A. Supplementary data
CCDC 1988080–1988085 contain the supplementary crystallographic data for 1–6. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/structures. Supplementary data to this article
can be found online at ...
References
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[3] Y. Yang, R. Ouyang, L. Xu, N. Guo, W. Li, K. Feng, L. Ouyang, Z. Yang, Y. Miao, J. Coord. Chem. 68
(2015) 379.
[4] H.L. Dupont. Drug Intell. Clin. Pharm. 21 (1987) 687.
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[6] T. Rhauderwiek, C. Cunha, H. Terraschke, N. Stock, Eur. J. Inorg. Chem. (2018) 3232.
[7] X.-P. Zhang, H.-R. Tian, G.-F. Yan, Y. Su, Y.-L. Feng, J.-W. Cheng, Dalton Trans. 42 (2013) 1088.
14

[8] A.C. Wibowo, M.D. Smith, H-C. Loye, Cryst. Growth Des. 11 (2011) 4449.
[9] Y.-Q. Sun, S.-Z. Ge, Q. Liu, J.-C. Zhong, Y.-P. Chen, CrystEngComm 15 (2013) 10188.
[10] B. Seyfried, B. Schink, Biodegradation 1 (1990) 1.
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[12] J.B. Lamture, Z.H. Zhou, A.S. Kumar, T.G. Wensel, Inorg. Chem. 34 (1995) 864.
[13] Rigaku Oxford Diffraction, CrysAlisPro Software System, Version 1.171.40.53, Rigaku
Corporation, Oxford, UK, 2019.
[14] G.M. Sheldrick, Acta Crystallogr. A: Found. Adv. 71 (2015) 3.
[15] G.M. Sheldrick, Acta Crystallogr. C: Struct. Chem. 71 (2015) 3.
[16] S. Parsons, H. D. Flack, T. Wagner, Acta Crystallogr. B: Struct. Sci., Cryst. Eng. Mater. 69
(2013) 249.
[17] A.L. Spek, Acta Crystallogr. C: Struct. Chem. 71 (2015) 9.
[18] A.D. Burrows, K. Cassar, R.M.W. Friend, M.F. Mahon, S.P. Rigby, J.E. Warren,
CrystEngComm 7 (2005) 548.
[19] A.F. Wells, Acta Crystallogr. 7 (1954) 534.
[20] V.A. Blatov, A.P. Shevchenko, D.M. Proserpio, Cryst. Growth Des. 14 (2014) 3576.
[21] J. Bernstein, R.E. Davis, L. Shimoni, N.-L. Chang, Angew. Chem. Int. Ed. Engl. 34 (1995) 1555.
[22] D.L. Kepert, in: S.J. Lippard (Ed.), Progress in Inorganic Chemistry, John Wiley & Sons, Inc.,
New York, 1978, Vol. 24, pp. 179-249.
[23] H. Aghabozorg, S. Kazemi, A.A. Agah, M. Mirzaei, B. Notash, Acta Crystallogr. E: Struct. Rep.
Online 67 (2011) m360.
[24] R. Kruszynski, T. Sierański, Cryst. Growth Des. 16 (2016) 587.
15

Table 1
Crystallographic data for 1–6.
Structure
Empirical formula
CCDC no.
Mr (g/mol)
T (K)
1
2
3
4
5
C22H28BiN5O12
C36H31BiN10O12
C48H63Bi2N9O26
C38H42Bi2N8O22
C38H46
763.47
1004.69
1600.03
1380.75
160(2)
1376.8
160(2)
Triclin
160(2)
160(2)
160(2)
Crystal system
Space group
Z
Monoclinic
I2
Monoclinic
I2/a
Monoclinic
I2/a
Triclinic
1
1
P
P
2
4
8
1
1
a (Å)
10.1017(2)
8.39850(10)
16.8625(3)
90
17.2134(3)
11.5660(3)
18.0478(4)
90
20.8376(3)
9.55920(10)
58.5817(8)
90
8.9911(3)
11.8703(4)
12.0770(4)
72.149(3)
69.948(3)
72.692(3)
1125.52(7)
Mo K, 0.71073
7.902
9.6056
12.109
12.123
69.554
67.031
73.066
1196.8
Mo K
7.427
b (Å)
c (Å)
 (°)
β (°)
104.716(2)
90
91.009(2)
90
95.5360(10)
90
 (°)
V (Å3)
1383.67(4)
Mo K, 0.71073
6.441
3592.58(14)
Mo K, 0.71073
4.990
11614.5(3)
Mo K, 0.71073
6.145
Radiation,  (Å)
 (mm-1)
Dcalc (Mg m-3)
Colour, habit
Crystal size (mm)
1.832
1.858
1.830
2.037
1.910
Colourless, block
0.26  0.10  0.05
2.7–29.5
Numerical
0.681, 1.000
15131
Colourless, needle
0.12  0.04  0.03
3.1–29.3
Spherical harmonics
0.913, 1.000
20971
Colourless, needle
0.20  0.07  0.04
2.1–28.5
Spherical harmonics
0.661, 1.000
103887
Colourless, block
0.18  0.10  0.06
2.7–29.5
Colour
0.09 
2.5–29
Spheri
0.753,
26563
5970
 range (°)
Absorption correction
Tmin, Tmax
Numerical
0.760, 1.000
24870
Reflections measured
Unique reflections
Rint
3472
4470
13517
5643
0.035
0.059
0.082
0.061
0.057
3472
3950
11019
5085
5053
Observed reflections [I > 2(I)]
Data, parameters, restraints
Goodness-of-fit on F2
R[F2 > 2(F2)]
wR(F2) (all data)
max, min (e Å-3)
3472, 229, 82
1.047
4470, 307, 202
1.132
13517, 936, 1279
1.154
5641, 358, 73
1.085
5970, 3
1.069
0.0218
0.0902
0.0702
0.0351
0.0349
0.0646
1.55, –
0.0512
0.2148
0.1551
0.0833
1.48, –0.86
10.37, –2.51
2.00, –1.96
2.40, –1.54
16

Table 2
Symmetry-unique bond distances (Å) around the central bismuth(III) centre in 1 and 2.
1
2
Bi1–O1
Bi1–O4i
Bi1–O6
Bi1–N1
2.516(4)
2.529(5)
2.334(5)
2.455(4)
2.466(9)
2.495(8)
2.411(9)
2.480(9)
Symmetry codes for O4i in 1: ½+x, ½+y, ½+z; in 2: 1-x, 1-y, 1-z.

Table 3
Hydrogen-bond parameters for 1–6.
D–H···A
Symmetry code for A D–H (Å)
H···A (Å)c
D···A (Å)
D–H···A (°)
1a
N2–H2A···O3
N2–H2B···O3
N3–H3A···O1
N3–H3B···O5
-½+x, ½+y, ½+z
-3/2-x. ½+y, -3/2-z
-1-x, -1+y, -1-z
0.91
0.91
0.91
0.91
2.01
1.84
1.97
2.06
140
166
147
174




2a
N2–H2···O1
N3–H31···O6
N3–H32···O5
N4–H4···O2
N5–H51···N5
N5–H52···O3
3/2-x. ½-y, -3/2-z
3/2-x. y, 1-z
0.88
0.88
0.88
0.88
0.88
0.88
1.90
2.14
2.13
1.91
2.43
2.37
167
163
164
151
130
139





x, 3/2-y, -½+z
x, 3/2-y, ½+z
½-x. y, 1-z

3a
O9–H9···O17
N5–H5A···O17
N5–H5B···O1
N6–H6A···O3
N6–H6B···O25
½+x, -y, z
x, 1+y, z
0.84
0.91
0.91
0.91
0.91
1.70
1.89
1.82
1.99
2.06
168
164
169
153
151





4
O8–H8···O5
O3–H3···O7
N4–H4A···O2
N4–H4B···O9
2-x, 1-y, 1-z
-1+x, 1+y, z
1-x, 2-y, -z
0.85(7)
0.92(7)
0.91
1.80(7)
1.67(7)
1.97
171(7)
172(7)
155




0.91
1.88
175
5
N3–H3A···O7
N3–H3B···O9
N4–H4A···O5
N4–H4B···O1
N6–H6A···O2
N6–H6B···O9
1+x, -1+y, z
1-x, -y, 1-z
-x, 1-y, 1-z
-1+x, y, z
0.88(6)
0.79(5)
0.87(5)
0.88(6)
0.91
2.00(6)
2.44(6)
2.10(5)
2.40(7)
1.91
169(5)
160(5)
164(5)
143(6)
160






1-x, -y, 2-z
0.91
1.91
175
6
N5–H5A···O9
N5–H5B···O4
N5–H5B···O5
0.88(3)
0.88(3)
0.88(3)
1.89(3)
2.08(4)
2.34(4)
2.763(3)
2.886(3)
3.109(3)
171(3)
152(3)
147(3)
x, 1+y, z
x, 1+y, z
a For disordered structures, only the parameters of the major conformation are listed.
18

Table 4
Geometric parameters of the π···π interactions in 2–6.
Ring 1a
Ring 2
Cg···Cg (Å) c
Distance
Slippage (Å)
 (°)d
between ring
planes (Å)
2b
N1
N2
N2
N1(1-x, 1-y, 1-z)
1.191
2.632
0.745
20.0
39.1
11.9




N2(3/2-x, ½-y, ½-z)
4.169(7)
N3(½+x, -½+y, -½+z) 3.625(8)
3b
N4
N4(1-x, 1-y, 1-z)
4.618(6)
2.583
34.0

4
N1
N1
N2
N1(-x, 2-y, 1-z)
N1(1-x, 2-y, 1-z)
N2(2-x, 1-y, 1-z)
4.822(3)
4.627(3)
3.972(2)
3.566
3.106
2.298
47.5
42.2
35.4



5
N1
N1
N2
N1(1-x, -y, 1-z)
N1(2-x, -y, 1-z)
N2(-x, 1-y, 1-z)
4.991(3)
5.321(3)
4.139(2)
3.366
4.415
2.527
42.4
56.1
37.6



6
N1
N2
N2
N1(1-x, -y, 1-z)
N2(1-x, 1-y, -z)
N2(2-x, 1-y, -z)
4.6271(12)
5.5964(13)
4.8590(13)
3.3512(9)
3.1172(9)
3.4305(9)
3.191
4.648
3.441
43.6
56.2
45.1
a The first two columns list the label of the N atom of the pyridine ring involved.
b For disordered structures, only the parameters of the major conformation are listed.
c Cg is the centre of gravity of a pyridine ring.
d  is the angle between the Cg···Cg vector and the normal to the ring planes.
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Table 5
Bond distances (Å) around each of the two bismuth(III) environments in 3a.
Bi1–O1
Bi1–O4i
Bi1–O6
Bi1–O7
Bi1–O12
Bi1–O16ii
Bi1–N1
Bi1–N2
2.483(6)
2.450(6)
2.345(6)
2.603(8)
2.242(7)
2.729(12)
2.459(7)
2.481(8)
Bi2–O7
2.540(8)
2.472(6)
2.531(12)
2.487(5)
2.470(6)
2.474(6)
2.500(7)
2.484(7)
Bi2–O13
Bi2–O15ii
Bi2–O18
Bi2–O19
Bi2–O24
Bi2–N3
Bi2–N4
Symmetry codes: (i) x, 1+y, z; (ii) x, -1+y, z.
a Only the distances for the major disorder conformation of Bi2 are shown; those from the minor conformation are
similar (restraints applied).
Table 6
Bond distances (Å) around the unique bismuth(III) centre in 4–6.
4
5
6
Bi1–O1
Bi1–O5
Bi1–O6
Bi1–O6i
Bi1–O9ii
Bi1–O10
Bi1–O11
Bi1–N1
Bi1–N2
2.464(3)
2.339(3)
2.686(3)
2.663(3)
–
2.548(3)
2.281(3)
2.609(3)
2.558(3)
–
2.2396(15)
2.5995(17)
2.2636(16)
–
2.9689(17)
2.6677(16)
2.5793(16)
2.3662(18)
2.4334(19)
2.289(3)
2.566(4)
2.387(4)
2.489(4)
2.336(3)
2.645(4)
2.366(3)
2.442(3)
Symmetry codes: (i) 1-x, 1-y, 1-z; (ii) 1-x, 1-y, -z.
CRediT authorship contribution statement
Levi Senior: Conceptualisation, Investigation, Methodology, Visualisation, Validation, Writing - original
draft. Anthony Linden: Conceptualisation, Supervision, Visualization, Validation, Writing - review &
editing, Project administration.
Declaration of interests
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☒ 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:
Three 1- and 2-dimensional bismuth-organic-frameworks have been synthesized from Bi2O3 and
2,4,6-pyridine tricarboxylic acid in the presence of a variety of additives. In contrast, replacement
of the 4-carboxy group with weaker donor groups results in discrete dinuclear anions.
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