Silver-based hybrid materials from meta or para phosphonobenzoic acid: Influence of the topology on silver release in water.

ABSTRACT


INTRODUCTION
Hybrid organic-inorganic materials have been extensively studied for their potential application in magnetism 1 , luminescence 2 , 3 , catalysis 4 and gas storage 5 .Biomedical applications constitute another field of development that currently focused many efforts of researchwhich is currently the focus of much research.Different kinds of hybrid materials that includeincluding sol-gel materials, 6 surface modified 7,8,9 inorganic nano-particles or crystalline MOF materials (coordination polymers or Metal Organic Frameworks materials) 10 were have been investigated as materials for drug delivery or diagnosis. 11,12Regarding crystalline hybrids, a firstearly strategiesy that was used to produce hybrid possessing the capability to release drug, wereas based on the intrinsic porosity of some materials that permitted their use as a reservoir of bioactive compounds including anti-thrombosis gas 13,14,15 , anti-inflammatory 16,17 or anti-cancer drugs. 18A secondLater approaches wereas based on the use of an active drug that acts as a building block (template) for the construction of biodegradable hybrids.Accordingly, the drug, or pro-drug, (e.g.peptide, 19 nicotinic acid 20 ) must possess a reactive functional groupity (e.g.carboxylate) that can interact with the inorganic network that is generated during the formation of the hybrid.In these two first strategies, the inorganic partner engaged in the structure of the hybrid must be as harmless as possible to avoid any side toxicity.A third further strategy consists of elaborate crystalline hybrids in which the inorganic part corresponds to the bio-active species.Following this strategy, the expected biological effects would arise from the release of the bio-active metallic salt into the surrounding media.It hasis indeed been established that some metallic salts and/or organometallic complexes may have biological effects including bactericidal 21,22,23 (e.g.Ag, Co, Cu) or anti-cancer actions 24,25 (e.g.Au, Ag…).The bactericidal action of silver salts, which likely is thought to arises from interaction with sulfur-containing proteins or binding to DNA, 26 was identified many years ago and recent developments have shown that organometallic silver-based compounds presented high bactericidal efficacies against gram negative bacterial strains. 27,28Crystalline coordination polymers were also studied for their potent bactericidal action.In this class of material most of the studies involved silver salts coordinated to aza-heterocyclic ligands (pyridyl, 29 pyrazolyl, 30 pyrazinyl 31 ).Recently we reported the first example of an efficient bactericidal silver-based hybrid in which phosphonic and carboxylate functional groups tether the organic part with the silver salt in a 3D arrangement. 32This work was carried out within a context that aimed to study that aimed to examine the use of rigid phosphonic acid derivatives 33 , 34 as building blocks for the construction of crystalline hybrids under hydrothermal conditions to produce fluorescent, 35 thermally stable 36 and non-centrosymmetic materials. 37,38For Through the study of the construction synthesis of silver-based hybrids we produced materials were produced with which couldthe potentially of acting as a reservoir of silver ions i.e. theyat could, via a disassembling of the hybrid in an aqueous media, exhibit bactericidal properties. 3129The basis of proposed mode of action via disassembly is rationalised e of this disassembling stands inby the fact that in these materials hard bases (carboxylate, phosphonic acids), according to Pearson HSAB theory 39,40 , are associated with a soft acid (silver salt).Accordingly, the expected low stability of such materials should leads to its degradation and the release of the bio-active silver ions when the material is placed in an hydrated aqueous environment.This scenario was indeed observed with Ag 6 (3-PO 3 -C 6 H 4 -COO) 2 (4) 41,3230 which released less than 2% of the silver present in the starting materials and that showed excellent bactericidal properties against clinically relevant Gram negative and Gram positive bacterial strains (including MRSA strains). 3129Other recent studies have also reported the bactericidal properties of cobalt 42 , silver 43,44 and copper-based 45 metal-organic-frameworks.In the recent study from Jones et al. 4441 , it was shown that the quantities of silver salts released in solution were almost identical irrespective of the structure of the polymeric material tested.More recently, silver-based materials synthesised from glutathione 46 , aminophosphinethiooxide 47 or aza-heteroaromatic compounds 3028,48,49 were reported and their anti-microbial activities were commented upon.In all these studies, each silver-based material exhibited bactericidal action when placed in aqueous solution.It is assumed that the release of silver salts into the surrounding aqueous media, which was quantified in some of these studies, is the most likely explaination for the antibacterial action.The controlled of the release of bioactive silver bioactive species therefore constitutes a key indicator with respect to potential biomedical applications.In the present study, we hypothesised that the topology of silver-based hybrid could may influence the silver release of silver ions into aqueous media.Herein, we report the synthesis of three new silver containing MOFs from two rigid di-functional organic precursors (3-phosphonobenzoic and 4-phosphonobenzoic acids).We have then subsequently quantified studied the silver-release capacities of these hybrid materials in aqueous media by the quantification by cathodic stripping voltammetry of the silver salts in water and demonstrate the relationship between topology and silver release in aqueous media as quantified by the amount of free silver ions present in water.
EXPERIMENTAL SECTION General 3-phosphonobenzoic 31 and 4-phosphonobenzoic 32 acids (Ffigure 1) were synthesized according to the reported methods.Elemental analyses were recorded with an automatic apparatus CHNS-O Thermo-Quest NA 2500.The Infrared spectroscopy (IR) spectra were recorded on a Perkin Fo rm a tted: Su p erscrip t Elmer spectrometer working in the transmittance mode, in the 450-4000 cm -1 range, at 4 cm -1 optical resolution.A pPowdered samples wereas diluted by mixing with KBr (2% wt).Thermo Gravimetric Analyses (TGA) were recorded with SETARAM TGA 92 apparatus.Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) have beenwere performed using a Zeiss supra 55 electron microscope.Silver concentration was determined by cathodic stripping voltammetry using Square wave mode and conducted with an µAutolabII equipment instrument (Metrohm).2), and Ag(3-PO 3 H-C 6 H 4 -COOH) (3) were obtained by hydrothermal synthesis according to the following reproducible method.Although the synthesis of compound 4 was already described elsewhere by Hix et al. 4139 we present here the conditions that achieved its synthesis according in a faster fashionin a shorter time and at a lower reaction temperature.For all syntheses, the pH of the synthesis media was measured after dispersion of the precursors in water (pH initial ) and directly at the end of the reaction (pH final ).These values are reported in Table 1.

Synthesis of Ag 3 (4-PO 3 -C 6 H 4 -COO) (1)
In a PTFE insert of 50 mL capacity, 3 equivalents of silver nitrate salt (AgNO 3 , 0.201 g, 1.2 mmol), 1 equivalent of 34-phosphonobenzoic acid (4-PO(OH) 2 -C 6 H 4 -COOH, 0.08 g, 0.4 mmol) and 1.5 equivalents of urea (CO(NH 2 ) 2 , 0.035g, 0.6 mmol) were dissolved in 15 mL of distilled water.This insert was placed in a Berghof pressure digestion vessel and heated from room temperature to 180°C in over X hours, maintained for 96 hours at 180°C and cooled to room temperature over 12 hours.The product was obtained as light brown needles, with suitable size
Final products obtained as white colourless needles with suitable size for structure resolution on by single crystal diffractions, were isolated by filtration, washed with water, rinsed with absolute ethanol and dried in air.

Hydrothermal synthesis of Ag 6 (3-PO 3 -C 6 H 4 -COO) 2 (4) by microwave heating
In a TFM insert of 100 mL capacity, 3 equivalents of silver nitrate salt (AgNO 3 , 0.201g, 1.2 mmol), 1 equivalent of 3-phosphonobeinzoic acid (3-PO(OH) 2 -C 6 H 4 -COOH, 0.08 g, 0.4 mmol) and 1.5 equivalents of urea (CO(NH 2 ) 2 , 0.035g, 0.6 mmol) were dissolved in 15 mL of distilled water.This insert was placed in a CEM MARS 5 microwave oven and heated from room temperature to 140°C over 1 hour, heated for 3 hours at 140°C and allowed to air cool to room temperature.The final product, obtained as light brown plates, with suitable size for structure resolution byof single crystal diffractions, was isolated by filtration, washed with water rinsed with absolute ethanol and dried in air.

Structural description of Ag 3 (4-PO 3 -C 6 H 4 -COO) (1), Ag(4-PO 3 H-C 6 H 4 -COOH) (2), and Ag(3-PO 3 H-C 6 H 4 -COOH) (3)
Single crystals of high crystalline quality and suitable size were selected using stereomicroscope.Details of the data collection for the samples 1, 2 and 3 are reported in Table 2.The Apex2 or EvalCCD 50 software suites were used to extract reflections from the collected frames and the intensities were corrected for absorption using the empirical method implemented in SADABS. 51Structural models considering the ad hoc space group has beenwere built up with SUPERFLIP 52 using the charge flipping method.The model was then introduced into the refinement programs; all the atomic positions were refined and then anisotropic displacement parameters (ADP) were considered for all the atoms (except for H atoms).The positions of the H atoms was were determined on geometrically considerations and restricted in bonds to their O or C nearest neighbor.It can be noted that the main residues in the electron density map are located in the vicinity of the Ag atoms.Atomic parameters for the samples 1, 2 and 3 are summarized in Tables Si-1, SI-3 and SI-5.The refinements of the structures were achieved with Jana2006 53 and OLEX2 54 software.

<< Table 1 >> Thermal Gravimetric Analysis (TGA)
In an alumina crucible, an accurate mass around 15 mg of crystalline samples were weighed and heated under air flow from 25°C to 1000°C at 3°C/min, left at 1000°C during 1 hour and then allowed to cool to room temperature.The mass lossest were recorded with a SETARAM TGA 92 apparatus (Ffigure 2).

Quantification of silver release in water
12 mg of a selected sample (compound 1-4) was suspended in 1 mL of distilled water.The sample is then maintained in the dark at room temperature.At different time points (t = 2h, 24h and 48h), 100 µL of the solution was taken up and immediately mixed with a calculated volume of potassium iodide water solution (C = 2.096 mM).This volume was examined as follows: the number of silver atoms presents in 12 mg of a selected materials (1-4) was calculated; the amount of KI added corresponded to 4 % of the number of silver atom previously calculated (this quantity of KI correspond to an excess when compared to the silver release in solution).The suspension was maintained in the dark until the quantification of the remaining iodide ions in solution by cathodic stripping voltammetry.This solution was diluted by a factor of 200 in water.Depending on the concentration of iodide in the sample a volume between 50 and 100 µL of the diluted solution was added to 20 mL of the electrolytic solution and the excess of iodide was determined by cathodic stripping voltammetry.
After degassing with nitrogen for 10 min, iodide was deposited onto the surface of a hanging mercury at -0.1V for 30s.The stirring was then stopped and after a rest period of 10 second the scan was initiated in the negative direction.Accordingly, the deposited mercurous iodide was reduced by the cathodic potential scan.Under our experimental conditions, 0.5M NaCl, 0.01M HEPES and triton 0.001% used as electrolytic solution, a current peak is observed at about -0.325 V referred with respect to to the Ag/AgCl/3M KCl reference electrode.A platinum wire is used as the auxiliary electrode.The following values experimental parameters were used: square wave modulation, pulse height 50 mV, step 1mV, frequency 50 Hz.At the beginning of each accumulation/ stripping cycle 5 mercury drops were discarded.Iodide was quantified by the standard addition method.Indirectly the concentrations of silver in solution were calculated.

RESULTS AND DISCUSSION
Phosphono-benzoic derivatives (Figure 1) constitute a unique class of rigid organic compounds which can be employed as precursors forof hybrid materials.Their rigidity provides some explaination for the production offact that they give rise to thermally stable materials 32 and in few cases non centro-symmetric materials 35 .These organic precursors, which can be synthesised at a multigram scale in 3 steps from the commercially available bromo-benzoic acid, must be also be classified in theas hetero-difunctional compounds in which both functional groups (phosphonic acid, carboxylic acid) can independently be used to connect the organic moiety to an inorganic network.More interestingly, we haveit has been previously shown that during the synthesis of hybrids under hydrothermal conditions, the chemoselectivity can be controlled by the pH of the reaction media.Indeed, at low pH, materials in which only the phosphonic acid functional groups were bonded to the inorganic network were produced while, at higher pH, the two functional groups were linked to the inorganic network thus producing 3D structures.These findings are also consistent with the work of Zhang et al that reported the effects of the pH on crystal size of some MOF materials. 55With the aim of following our previous study reporting the ability of compound 4, (Ag 6 (4-PO 3 -C 6 H 4 -COO) 2 ), to release silver ions and to act as an efficient bactericidal material, 30 we investigated herein whether the chemoselectivity principle, previously observed with copper, -based materials, could be also applied to silver-based hybrids.
Accordingly to this approach, we expected to produce silver-based hybrids with different topologies, that couldwhich might then exhibit different silver release properties when placed in aqueous media.Such modulation of the silver release might open new perspectives for the use of such type of hybrid materials as bactericidal agents.In this study, two organic precursors (3phosphonobenzoic and 4-phosphonobenzoic) were used as organic precursors of hybrids (figure 1).For the synthesis of the hybrid materials 1-3, hydrothermal synthesis were used (140°C , 12 or 24 hours) in presence or absence of urea as summarized in table 1.

Thermal analysis
Thermo Gravimetric Analyses (TGA) were recorded in order to confirm the absence of water molecules in the structure of each compound and to determine their thermal stability.The analyses were recorded in air flow from 25°C to 1000°C (Ffigure 2).As expected, no mass lost was observed for these compounds from room temperature to 360°C thus confirming the data obtained by X-ray diffraction that concluded on the absence ofthat no water molecules were present in the structures.These analyses also showed the high thermal stability of this series of compounds up to 300°C.Above 360°C several weight losses were observed which can be attributed to the degradation of the organic network.The weight losses recorded at 600°C for (2)   and ( 3) which are respectively of 41.6% and 40.76%, are in good agreement with weight loss expected to the formation of the silver phosphate AgPO 3 .Concerning ( 1) and ( 4) the weight loss of 21% recorded respectively at 579°C and 550°C is in good agreement with the expected value corresponding to the formation of silver phosphate Ag 3 PO 4 .After further heating the final product of this thermal decomposition obtained as pellet was identified by X-ray diffraction as silver metal for (3) (Ag, cubic, Fm-3m, a4.087Å)(Figure SI-7).
They exhibit a lamellar structure consisting of regular intergrowth of inorganic and organic layers. 3331,56The main difference in between these three materials is related to the structure of the organic layers; the organic slabs exhibit a thickness corresponding either to one phosphonobenzoate group (i.e.~10Å) or to the stacking of two phosphonobenzoic groups (i.e.~16Å).Following this observation, compounds (1), ( 2) and (3) can be sorted described as a function of the architecture of the organic part: single or double slab.
The structure of Ag 3 (4-PO 3 -C 6 H 4 -COO) (1) first layered architecture is characterized by an organic slab with a thickness ~10Å corresponding to one a single 4-phosphonobenzoate group Fo rm a tted: Fo n t: Italic (i.e.~10Å); Ag 3 (4-PO 3 -C 6 H 4 -COO) (1) compound is associated to this class.Its main characteristics are reported in the Table 1.In Figures 3 and 4  O 3 ) and (Ag 1 and O 2 )) are at an angle of 62.677° with respect to one another.Finally, to confirm that the crystal structures obtained by single crystal X-ray diffraction were representative of the whole sample, powder X-ray diffraction were recorded from powder of ground crystals.As shown in figures SI-1, SI-2 and SI-3 good fits were obtained between powder diffraction and simulation of powder diffraction form single crystal X-ray data.
Pictures recorded by scanning electron microscopy (SEM) confirmed the homogeneity of the samples (1), ( 2) and (3).These three samples exhibited platelet shape as shown in the supporting materials (SI 4-6).
With four silver-based metal organic materials, including the three new materials 1, 2 and 3, we studied their capacity to release silver ions when these materials were placed in water was studied.In view of the crystal structure of these materials we might expect to observe different behaviors in terms of silver release.We have previously reported that compound 4 was able to releases silver ions; this silver release accounted for the bactericidal property of this material against six different bacterial strains 3231 .The new materials 1, 2 and 3 were tested as potential reservoirs of silver ions using the same experimental setupprocedure.In view of the crystal structure of these materials we could expect to observe different behaviors in terms of silver release.Among the different methods frequently used to determine low concentration of silver in water solution, cathodic stripping voltammetry is a very sensitive and highly reliable method. 58e silver-based hybrid materials (1), (2) and (3) were suspended in water solution (see experimental part) and aliquots were taken up at different times and mixed with an aqueous potassium iodide water solution of known concentration.Then, the silver concentrations were indirectly determined by cathodic stripping voltammetry.The results, that also includinge the value when compound (4), used here for comparative purpose, was placed in water, are summarized in Figure 6.Firstly, it was observed that the quantities of silver released into water aqueous solution were very different and dependeding on the structure of the hybrid.Indeed, the more condensed material (1), in which the carboxylic and the phosphonic acid (para relative

Field Co de Cha ng ed
Fo rm a tted: Fo n t: (D efau lt) Times position on the benzene ring) were both engaged in iono-covalent bonds with the inorganic network, exhibited only traces of silver ions in water solution after an immersion period of two days.In comparison, compound (4), which was previously studied, exhibited a higher release despite the fact that at in this material the two functional groups (carboxylic and phosphonic acid in a meta relative position on the benzene ring) were are also engaged connected to the inorganic network.As shown ion Figure 3, the structure of compound (1) seems to be denser than that of compound (3) or (4). 3230This observation is confirmed by the value of the calculated densitiesy (Table 1) which areis respectively 3.78, 2.43 and 3.63 g/cm 3 for (1), ( 3) and (4).respectively.
With respect to the silver ion release capacity, the more open structure of compound (4), is the likely reason of its higher capacity to release silver ions in water solution when compared to compound (1).For the materials ( 2) and ( 3), in which only the phosphonic acid functional group is linked to the inorganic network, the quantity of silver the released in water was profoundly increased when compared to the behavior of materials (1) and ( 4).This result could be explained by the presence of free carboxylic acid functional groups within the structure that could favor the initial hydration of the materials (2) and (3)leading to an enhancement in their solubility.Moreover, it is likely that the stability of these hybrids towards dissolution in polar solvents was is dependent on the number of functional groups that are connected with the inorganic network.
In other words, this can be view as a stabilization by a cooperative effect.Another noticeable point to note concerns regards the kinetics of release.Indeed,It can be observed that the silver concentration in water solution (Figure 6) reached a plateau after 2h for compounds (2), ( 3) and (4).This observation could be explained by an equilibrium that involves the silver ion in solution and the silver ion immobilized at the surface of the hybrid materials.We have previously shown that this equilibrium can be shifted towards the dissolution of the hybrid in water by a successive replacement of the supernatant water solution by fresh water solution. 30Altogether, these results suggest that the hybrid materials can act as a reservoirs of silver ions.The release process likely occursred at the interface of the solid and water solution leading untilto reach an equilibrium is reached.Finally, the amount of silver release in solution depends on the structure of the hybrid, thus demonstrating that the topology of the hybrid material can be used to design materials possessing a tunable capability of releasing silver ions in its aqueous environment.

CONCLUSION
Three new silver-based metal organic frameworks were synthesised and fully structurally characterized.These hybrid materials were synthesised from either 3-phosphonobenzoic and 4phosphonobenzoic acids and silver nitrate under hydrothermal conditions.We evidenced fFor these silver-based MOFs, as we previously reported for other copper and zinc-based metal organic frameworks, that the pH of the reaction media is a key factor that which explainsed the chemoselectivity observed during the construction formation of the hybrid.Indeed, atAt low pH only the more acidic phosphonic acid is bonded to the inorganic network as in compound (2) and (3).On the other hand, the addition of urea in the pressure vessel, increased the pH thus producing a hybrid in which both functional groups were connected via iono-covalent bonds to the inorganic network as illustrated with compound (1).These results also demonstrate the interest of using heterodifunctional organic precursors since hybrids with different topologies can be produced by simply adapting altering the pH of the reaction media.The silver ion release (3) (Ag(3-PO 3 H -C 6 H 4 -COOH)), characterized by the presence of free carboxylic acid functional groups in their structure, released more easily silver salts in water.These results, concomitantly with the silver release capacity of material (4) previously reported, clearly show that the silver release is dictated by the topology of the hybrid.Accordingly, the silver release capacity in a surrounding aqueous solution can be tune by designing hybrids with an adapted structure as exemplified in this study.

ASSOCIATED CONTENT
Crystallographic data positional parameters and hydrogen bonds length and angle for compounds (1), ( 2) and ( 3) are available free of charge via the Internet at http://pubs.acs.org.Fo rm a tted: Su p erscrip t      Three new silver-based metal organic framework materials were prepared from either 4phosphonobenzoic acid or 3-phosphonobenzoic acid.These materials exhibit different topologies that are governed by the structure of the rigid organic precursor and the hydrothermal synthetic conditions.It is shown that the silver release of these materials placed in water, deeply depend on their topology thus opening the way to the conception of material for the control release of silver ions.

Figures and Tables
Graphical abstract REFERENCES
the projections of the structure along b and c directions are shown.The organic slab is constructed from 4-phosphonobenzoic groups; both phosphonate and carboxylate functions are involved in the bonding scheme with the Ag atoms; the result is that each the 4-phosphobenzoic groups is bridgeing two successive inorganic layers.The three oxygen atoms of the phosphonate ending are bonded to three Ag atoms while those of the carboxylate groups are bonded to two Ag atoms.It can be noted that within an organic slab all the 4-phosphonobenzoate groups exhibit head to tail organization along a and b.Owing to this specific organization, the inorganic slabs show stack in the c direction aeach having a double layer configuration resulting in from the stacking of two adjacent single layers as shown in the Figure 5.The oxygen environments of Ag1 and Ag2 defines a distorted tetrahedron with the silver located at the center of one face of the polyhedron.Ag3 is surrounded by three nearest neighbor O atoms and is theus located at the center of a triangular plane.The Ag-O distances range from 2.2 to 2.6 Å.Two Ag1O 4 (or Ag2O 4 ) tetrahedra share one edge and form an Ag 2 O 6 unit.This unit shares edges with four4 PO 3 C tetrahedra, with one Ag 2 O 6 and three3 Ag 3 O 3 units.The main interatomic distances are summarized in Table SI-2.<< Figure 3>> and <<Figure 4>> and <<Figure 5>> The second layered architecture is characterized by an organic slab with a thickness of~16Å corresponding to the stacking of two phosphonobenzoic groups (i.e.~16Å); the Ag(4-PO 3 H-C 6 H 4 -COOH) (2) and Ag(3-PO 3 H-C 6 H 4 -COOH) (3) compounds are associated to this second classboth crystallise with this type of layer structure.The main characteristics of these two materials are reported in the Table SI-2 and SI-5.Contrarily to what is occurring inin the Fo rm a tted: No t Su p erscrip t/ Su b scrip t situation for the materials (1), only the phosphonic acid groups are implied involved in the bonding with the Ag atoms.As a consequence, the organic slab of (2) and (3) is constructed from dimers formed by two phosphonobenzoic groups connected together via hydrogen bonds involving the free carboxylic acid functions.As revealed by the crystallographic study, two oxygen atoms of the phosphonate group take part to the chemical bond with Ag; one of the acid functions is not fully deprotonated.In Ag(4-PO 3 H-C 6 H 4 -COOH) (2), the silver (I) atoms are surrounded by four oxygen atoms and the Ag-O distances is ranged from 2.30 to 2.46 Å; the resulting coordination is thuis a distorted tetrahedron.Each edge of this AgO 4 tetrahedron is connected to one HPO 3 C and to one AgO 4 polyhedrona.For the second compound Ag(3-PO 3 H -C 6 H 4 -COOH) (3) the inorganic sub network is constituted comprised of Ag + cations which have a very highly distorted tetrahedral coordination geometry.As for the previous compound, the silver cations are surrounded by the four oxygen atoms of thefrom phosphonate functiongroups.The distance between the Ag + cations and the coordinating oxygen atoms range from 2.28 to 2.56 Å and are slight greater than the distances observed for (2).The observed distorted polyhedra are connected together via one edge to form [AgO 2 ]  parallel chains running along the a + b direction.These chains are separated by the PO 3 C groups; and the structure of one chain is similar to the structure of the tetranuclear unit {Ag 4 O 6 } described by Zheng et al. 57 in the silver (I) pyrophosphonates Ag 2 (ptp) and Ag 2 (ppp) with [ptp 2-= pyro-3-thienylphosphonate, ppp 2-= pyrophenylphosphonate.In one chain of compound (3), the planes passing through two successive motifs (made of the atoms (Ag 1 and capability was then tested by placing these materials in water solution.The silver ion concentration in supernatant solution was determined by cathodic stripping voltammetry.It was shown that materials (1) (Ag 3 (4-PO 3 -C 6 H 4 -COO), which exhibited the more compact structure released only traces of silver ions in solution while materials (2) (Ag (4-PO 3 H-C 6 H 4 -COOH) and

Figure 4 :
Figure 4: Projection along c of inorganic slab of 1, 2 and 3. Blue, red and white spheres correspond to Ag, O, and H atoms respectively PO 3 C groups are drawn using green tetrahedra.

Figure 5 :
Figure 5: Projection along c of the single layers at z~0.06 and z~-0.06 for the structure of 1

Figure 6 :
Figure 6: Concentration (mM) of Ag + in solution as a function of time when 12 mg of a selected material (1-4) was placed in 1 mL of water (t=6h corresponds to the first analysis).

Table 2 Sample 1
Chemical formula Ag 3 (4-PO 3 -C 6 H 4 -COO) Ag(4-PO 3 H-C 6 H 4 -COOH) Ag(3-PO 3 H-C 6 H 4 -COOH) Fo rm a tted: Fo n t: 10 p t, No t Su p erscrip t/ Su b scrip t Fo rm a tted: Fo n t: 10 pt Fo rm a tted: Fo n t: 10 p t, No t Su p erscrip t/ Su b scrip t Fo rm a tted: Su p erscrip t