Correction to "Structural Landscape of α-Acetamidocinnamic Acid Cocrystals with Bipyridine-Based Coformers: Influence of Crystal Packing on Their Thermal and Photophysical Properties".

[This corrects the article DOI: 10.1021/acs.cgd.3c01374.].

Structural Landscape of α-Acetamidocinnamic Acid Cocrystals with Bipyridine-Based Coformers: Influence of Crystal Packing on Their Thermal and Photophysical Properties.

Controlling the supramolecular synthon outcome in systems with different functionalities has been a key factor for the design of supramolecular materials, which also affected their physicochemical properties. In this contribution, we have analyzed the structural landscape of α-acetamidocinnamic acid (HACA) aiming to find its synthon outcome from the competitivity between its acidic and amidic groups. We prepared four multicomponent forms including one dihydrate (HACA·2H2O) and three cocrystals bearing different bipyridine coformers with formulas (HACA)2(1,2-bpe) (1), (HACA)2(4,4'-azpy) (2), and (HACA)2(4,4'-bipy)3 (3) (1,2-bpe = 1,2-bis(4-pyridyl)ethylene; 4,4'-azpy = 4,4'-azopyridine; 4,4'-bipy = 4,4'-bipyridine). First, we applied a virtual screening approach to assess the feasibility of cocrystal formation. Then, we synthesized the cocrystals, via liquid-assisted grinding (LAG) (1 and 2) or solvothermal (3) techniques, and single crystals of HACA, and their four multicomponent forms were obtained showing different synthons and crystal packings. Besides, a Cambridge Structural Database (CSD) search of the cocrystals presenting bipyridine-type coformers and molecules with acid and amide functionalities was performed, and the observed synthon occurrences as well as the possibility of synthon modification by tuning the H-donor/H-acceptor propensity of the acidic and amidic groups were shown. Finally, we measured their thermal and photophysical properties, which were correlated with their structural features.

The Formation of a Unique 2D Isonicotinate Polymer Driven by Cu(II) Aerobic Oxidation.

The isolation and structural characterization of a unique Cu(II) isonicotinate (ina) material with 4-acetylpyridine (4-acpy) is provided. The formation of [Cu(ina)2(4-acpy)]n (1) is triggered by the Cu(II) aerobic oxidation of 4-acpy using O2. This gradual formation of ina led to its restrained incorporation and hindered the full displacement of 4-acpy. As a result, 1 is the first example of a 2D layer assembled by an ina ligand capped by a monodentate pyridine ligand. The Cu(II)-mediated aerobic oxidation with O2 was previously demonstrated for aryl methyl ketones, but we extend the applicability of this methodology to heteroaromatic rings, which has not been tested so far. The formation of ina has been identified by 1H NMR, thus demonstrating the feasible but strained formation of ina from 4-acpy in the mild conditions from which 1 was obtained.

Amide-Driven Secondary Building Unit Structural Transformations between Zn(II) Coordination Polymers.

The behavior of coordination polymers (CPs) against external stimuli has witnessed remarkable attention, especially when the resulting CPs present reversible molecular arrays. Accordingly, CPs with these characteristics can lead to differences in their properties owing to these structural differences, being promising for their use as potential molecular switches with diverse applications. Herein, we have synthesized four Zn(II) CPs bearing α-acetamidocinnamic acid (HACA) and 4,4'-bipyridine (4,4'-bipy). The reaction between Zn(OAc)2·2H2O, HACA, and 4,4'-bipy yields {[Zn(ACA)2(4,4'-bipy)]·EtOH} n (1), which was used for the formation of three CPs through dissolution-recrystallization structural transformations (DRSTs): {[Zn(ACA)2(4,4'-bipy)]·2MeOH} n (2), {[Zn2(µ-ACA)2(ACA)2(4,4'-bipy)]·2H2O} n (3), and {[Zn3(µ-ACA)6(4,4'-bipy)]·0.75CHCl3} n (4). The study of the four crystal structures revealed that their secondary building units (SBUs) comprise monomeric, dimeric, and trimeric arrangements linked by 4,4'-bipy ligands. The fundamental role of the utilized solvent and/or temperature, as well as their effect on the orientation of the amide moieties driving the formation of the different SBUs is discussed. Furthermore, the reversibility and interconversion between the four CPs have been assayed. Finally, their solid-state photoluminescence has evinced that the effect of the amide moieties not only predetermine a different SBU but also lead to a different emission in 4 compared with 1-3.

Controlling the Formation of Two Concomitant Polymorphs in Hg(II) Coordination Polymers.

Controlling the formation of the desired product in the appropriate crystalline form is the fundamental breakthrough of crystal engineering. On that basis, the preferential formation between polymorphic forms, which are referred to as different assemblies achieved by changing the disposition or arrangement of the forming units within the crystalline structure, is one of the most challenging topics still to be understood. Herein, we have observed the formation of two concomitant polymorphs with general formula {[Hg(Pip)2(4,4'-bipy)]·DMF}n (P1A, P1B; Pip = piperonylic acid; 4,4'-bipy = 4,4'-bipyridine). Besides, [Hg(Pip)2(4,4'-bipy)]n (2) has been achieved during the attempts to isolate these polymorphs. The selective synthesis of P1A and P1B has been successfully achieved by changing the synthetic conditions. The formation of each polymorphic form has been ensured by unit cell measurements and decomposition temperature. The elucidation of their crystal structure revealed P1A and P1B as polymorphs, which originates from the Hg(II) cores and intermolecular associations, especially pinpointed by Hg···π and π···π interactions. Density functional theory (DFT) calculations suggest that P1B, which shows Hg(II) geometries that are further from ideality, is more stable than P1A by 13 kJ·mol-1 per [Hg(Pip)2(4,4'-bipy)]·DMF formula unit, and this larger stability of P1B arises mainly from metal···π and π···π interactions between chains. As a result, these structural modifications lead to significant variations of their solid-state photoluminescence.

Tuning Photophysical Properties by p-Functional Groups in Zn(II) and Cd(II) Complexes with Piperonylic Acid.

Aggregation between discrete molecules is an essential factor to prevent aggregation-caused quenching (ACQ). Indeed, functional groups capable of generating strong hydrogen bonds are likely to assemble and cause ACQ and photoinduced electron transfer processes. Thus, it is possible to compare absorption and emission properties by incorporating two ligands with a different bias toward intra- and intermolecular interactions that can induce a specific structural arrangement. In parallel, the π electron-donor or electron-withdrawing character of the functional groups could modify the Highest Ocuppied Molecular Orbital (HOMO)-Lowest Unocuppied Molecular Orbital (LUMO) energy gap. Reactions of M(OAc)2·2H2O (M = Zn(II) and Cd(II); OAc = acetate) with 1,3-benzodioxole-5-carboxylic acid (Piperonylic acid, HPip) and 4-acetylpyridine (4-Acpy) or isonicotinamide (Isn) resulted in the formation of four complexes. The elucidation of their crystal structure showed the formation of one paddle-wheel [Zn(µ-Pip)2(4-Acpy)]2 (1); a mixture of one dimer and two monomers [Zn(µ-Pip)(Pip)(Isn)2]2·2[Zn(Pip)2(HPip)(Isn)]·2MeOH (2); and two dimers [Cd(µ-Pip)(Pip)(4-Acpy)2]2 (3) and [Cd(µ-Pip)(Pip)(Isn)2]2·MeOH (4). They exhibit bridged (1, µ2-η1:η1), bridged, chelated and monodentated (2, µ2-η1:η1, µ1-η1:η1 and µ1-η1), or simultaneously bridged and chelated (3 and 4, µ2-η2:η1) coordination modes. Zn(II) centers accommodate coordination numbers 5 and 6, whereas Cd(II) presents coordination number 7. We have related their photophysical properties and fluorescence quantum yields with their geometric variations and interactions supported by TD-DFT calculations.

Steric and Electronic Effects on the Structure and Photophysical Properties of Hg(II) Complexes.

Since many factors influence the coordination around a metal center, steric and electronic effects of the ligands mainly determine the connectivity and, thus, the final arrangement. This is emphasized on Hg(II) centers, which have a zero point stabilization energy and, thus, a flexible coordination environment. Therefore, the unrestricted Hg(II) geometry facilitates the predominance of the ligands during the structural inception. Herein, we synthesized and characterized a series of six Hg(II) complexes with general formula (Hg(Pip)2(dPy)) (Pip = piperonylate, dPy = 3-phenylpyridine (3-phpy) (1), 4-phenylpyridine (4-phpy) (2), 2,2'-bipyridine (2,2'-bipy) (3), 1,10-phenanthroline (1,10-phen) (4), 2,2':6',2'-terpyridine (terpy) (5), or di(2-picolyl)amine (dpa) (6)). The elucidation of their crystal structures revealed the arrangement of three monomers (3, 5, and 6), one dimer (4), and two coordination polymers (1 and 2) depending on the steric requirements of the dPy and predominance of the ligands. Besides, the study of their photophysical properties in solution supported by TD-DFT calculations enabled us to understand their electronic effects and the influence of the structural arrangement on them.

Influence of Aromatic Cations on the Structural Arrangement of Hg(II) Halides.

Understanding the structure and arrangement of hybrid metal halides and their contribution to the optoelectronic properties is, thus far, a challenging topic. In particular, new materials composed of d10 metal halides and pyridinium cations are still largely unexplored. Therefore, we report the synthesis and characterization of six Hg(II) salts built up from (Hg2Cl6)2- or (HgX4)2- anions (X = Cl, Br, I) and 2,2'-bipyridium (2,2'-Hbipy)+, 2,2'-bipyridine-1,1'-diium (2,2'-H2bipy)2+, or 1,10-phenantrolinium (1,10-Hphen)+ cations, using the same experimental conditions. All of them have been characterized by PXRD, EA, FTIR-ATR, and 1H NMR spectroscopies; single-crystal X-ray diffraction; and TG/DTA determinations. The study of their packing via Hirshfeld surface analysis and 3D deformation density mapping revealed the contributions of the intermolecular interactions to the structural arrangement, notably, the effect of the cation planarity on them. Successively, periodic DFT calculations showed that (i) the valence and conducting bands are mainly composed of the p orbitals of the halide and the organic cation, respectively, and (ii) the corresponding band gap depends mainly on the halide.

Construction of Zn(II) Linear Trinuclear Secondary Building Units from A Coordination Polymer Based on α-Acetamidocinnamic Acid and 4-Phenylpyridine.

The synthesis and characterization of one coordination polymer and two trinuclear complexes are presented. The coordination polymer [Zn2(µ-O,O'-ACA)2(ACA)2(4-Phpy)2]n (1) has been obtained by the reaction between Zn(OAc)2·2H2O, α-acetamidocinnamic acid (HACA), and 4-phenylpyridine (4-Phpy) using EtOH as solvent. Its recrystallization in CH3CN or EtOH yields two trinuclear complexes, both having pinwheel arrays with formulas [Zn3(µ-ACA)6(4-Phpy)2]·4CH3CN (2·4CH3CN) and [Zn3(µ-ACA)6(EtOH)2]·4EtOH (3·4EtOH), respectively. These trinuclear species, unavoidably lose their solvent co-crystallized molecules at RT yielding the complexes [Zn3(µ-ACA)6(4-Phpy)2] (2) and [Zn3(µ-ACA)6(EtOH)2] (3). In addition, compound 2 has also been obtained reacting Zn(OAc)2·2H2O, HACA, and 4-Phpy in a 1:2:2 ratio using CH3CN as solvent. Compounds 1-3 have been characterized by analytical and spectroscopic techniques. Furthermore, single crystals suitable for X-ray diffraction method for compounds 1, 2·4CH3CN, and 3·4EtOH were obtained and their supramolecular interactions have been studied and discussed, showing 2D supramolecular planes for the trinuclear complexes and a 3D supramolecular network for the coordination polymer. Finally, the supramolecular interactions of 2·4CH3CN and 3·4EtOH have been compared using Hirshfeld surface analysis and electrostatic potential calculations.

Isonicotinamide-Based Compounds: From Cocrystal to Polymer.

The reaction between [Cu(µ-OAc)(µ-Pip)(MeOH)]2 (1) (OAc = acetate; Pip = 1,3-benzodioxole-5-carboxylate) and isonicotinamide (Isn) in MeOH as solvent yielded two mixture pairs of three compounds: {(HPip)2(Isn) (2), [Cu(Pip)2(Isn)2] (3)} and {(3), {[Cu3(Pip)2(OAc)2(µ-Isn)2(Isn)2(µ-OCH3)2(MeOH)2]·2MeOH}n (4)}. Modifying the reaction conditions (t, T, molar ratio), 2 and 3 have been successfully isolated, whereas 3 and 4 had to be mechanically separated. The recrystallization of 3 in pentanol yielded single crystals of compound [Cu(Pip)2(Isn)2]·C5H11OH (3a). The X-ray crystal structure of 2, 3a, and 4 has been elucidated showing a cocrystal, a monomer, and an unusual coordination polymer, respectively. The Pip ligand exhibited a chelate (3a) or a monodentate (4) coordination mode, but the Isonicotinamide (Isn) ligand is the one that promoted the arrangement of different structures and also mainly directs the formation of the 2D and 3D supramolecular assemblies. All the structures have been analyzed by Hirshfeld surface. In addition, the energy frameworks and lattice energy values of 2 and 3a have been calculated.

Modulating p-hydroxycinnamate behavior as a ditopic linker or photoacid in copper(ii) complexes with an auxiliary pyridine ligand.

The reaction of copper(ii) acetate monohydrate with p-hydroxycinnamic acid (HpOHcinn) and different pyridine derivatives (4-tert-butylpyridine, 4-tBupy; 4-acetylpyridine, 4-Acpy; 3-phenylpyridine, 3-Phpy; 4-phenylpyridine, 4-Phpy) was essayed in methanol solvent at room temperature. The crystal structures of the resulting compounds were elucidated. Their analysis shows that the choice of pyridine ligands determines different coordination modes of the pOHcinn ligand and the Cu(ii) coordination, nuclearity and geometry. The pOHcinn acts as a monodentate carboxylate ligand in combination with 4-tBupy or 4-Phpy, yielding monomers and dimers, associated by hydrogen bonds into supramolecular networks in which the phenol group plays a key role. Conversely, in combination with 4-Acpy or 3-Phpy, the phenol group coordinates directly to the Cu(ii), acting as a ditopic ligand and yielding 2D coordination polymers. The compound containing 3-Phpy shows interesting MeOH-H2O reversible exchange behavior. Not only has the pyridine auxiliary ligand had a tremendous effect on the coordination mode of pOHcinn, but also its reactivity is influenced. Particularly, in the case of the compound containing 4-Phpy, it undergoes a photoinduced process, in which the phenol group deprotonates and coordinates to Cu(ii) as a phenoxy ligand. This yields a coordination polymer in which two different dimers alternate, bridged by the resulting pOcinn ligand. The magneto-structural correlation of this compound is also discussed.

An integrated phenol 'sensoremoval' microfluidic nanostructured platform.

Phenol is a widely used chemical that for several reasons may be released into the environment and, consequently, its detection and subsequent destruction into the ground and surface waters are of special importance. Herein, a simple lab-on-a-chip (LOC) device based on biocompatible and biodegradable CaCO3- poly(ethyleneimine) (PEI) nanostructured microparticles (MPs) to detect and remove phenolic wastes is proposed. The detection of phenol using a hybrid polydimethylsiloxane (PDMS)/glass chronoimpedimetric microchip and its removal in the same LOC system through the use of an extra CaCO3-PEI MPs microcolumn is achieved. For the first time, the chronoimpedance technique is applied in a LOC system for phenol sensing in a range of 0.01-10 µM achieving the limit of detection (LOD) of 4.64 nM. Moreover, this device shows a high repeatability with a relative standard deviation of 3% which is almost 4 times lower than that for the chronoamperometry technique. This LOC system represents an integrated platform for phenol sensing and removal (sensoremoval) that can be easily fabricated and is of a low cost, disposable and amenable to mass production.

Nanostructured CaCO3-poly(ethyleneimine) microparticles for phenol sensing in fluidic microsystem.

A new and simple strategy based on nanostructured CaCO3-poly(ethyleneimine) (PEI) microparticles (MPs) for phenol sensing using PDMS/glass fluidic microchip is developed. This fluidic microsystem including integrated screen-printed electrodes modified with CaCO3-PEI MPs and tyrosinase (Tyr) through cross-linking with glutaraldehyde, represents a low-cost platform for phenol detection. The designed fluidic microsystem improves the sensitivity of the biosensor allowing the detection of very low concentrations of phenol (up to 10 nM). This device shows high repeatability and low detection limit, is easy to be fabricated, inexpensive, disposable, and amenable to mass production.

High sensitive gold-nanoparticle based lateral flow Immunodevice for Cd2+ detection in drinking waters.

In this work for first time a lateral flow immunosensor device (LFID) for Cd(2+) determination in drinking and tap waters using the Cd-EDTA-BSA-AuNP conjugate as signal producer tool is introduced. The principle of working is based on competitive reaction between the Cd-EDTA-BSA-AuNP conjugate deposited on the conjugation pad strip and the Cd-EDTA complex formed in the analysis sample for the same binding sites of the 2A81G5 monoclonal antibody, specific to Cd-EDTA but not Cd(2+) free, which is immobilized onto the test line. The device has a large response range within 0.4-2000ppb, being the linear response between 0.4 and 10ppb. The quantification and detection limits of 0.4 and 0.1ppb, respectively, represent the lowest ones reported so far for paper based metal sensors. The obtained detection limit is 50 times lower than the maximum contamination level required for drinking water. Here we also show a new option for increasing the sensibility in the LFDs with competitive format, through the decreasing in concentrations of the Cd-EDTA-BSA-AuNP conjugate deposited in the conjugation strip and the mAbs deposited in the test and control zones until to reach optimized concentrations. It is an important result take into account that the increase in sensibility is one of the challenges in the field of LFD sensors, where are focused many of the ongoing researches. In addition, a specificity study of the device for several metal interferences, where potential metal interferences are masked with the use of the EDTA and OVA optimized concentrations, is presented too.

All-integrated and highly sensitive paper based device with sample treatment platform for Cd2+ immunodetection in drinking/tap waters.

Nowadays, the development of systems, devices, or methods that integrate several process steps into one multifunctional step for clinical, environmental, or industrial purposes constitutes a challenge for many ongoing research projects. Here, we present a new integrated paper based cadmium (Cd(2+)) immunosensing system in lateral flow format, which integrates the sample treatment process with the analyte detection process. The principle of Cd(2+) detection is based on competitive reaction between the cadmium-ethylenediaminetetraacetic acid-bovine serum albumin-gold nanoparticles (Cd-EDTA-BSA-AuNP) conjugate deposited on the conjugation pad strip and the Cd-EDTA complex formed in the analysis sample for the same binding sites of the 2A81G5 monoclonal antibody (mAb), specific to Cd-EDTA but not Cd(2+) free, which is immobilized onto the test line. This platform operates without any sample pretreatment step for Cd(2+) detection thanks to an extra conjugation pad that ensures Cd(2+) complexation with EDTA and interference masking through ovalbumin (OVA). The detection and quantification limits found for the device were 0.1 and 0.4 ppb, respectively, these being the lowest limits reported up to now for metal sensors based on paper. The accuracy of the device was evaluated by addition of known quantities of Cd(2+) to different drinking water samples and subsequent Cd(2+) content analysis. Sample recoveries ranged from 95 to 105% and the coefficient of variation for the intermediate precision assay was less than 10%. In addition, the results obtained here were compared with those obtained with the well-established inductively coupled plasma emission spectroscopy (ICPES) and the analysis of certificate standard samples.

Ion-directed assembly of gold nanorods: a strategy for mercury detection.

Water-soluble gold nanorods (Au NRs) have been functionalized with an N-alkylaminopyrazole ligand, 1-[2-(octylamino)ethyl]-3,5-diphenylpyrazole (PyL), that has been demonstrated able to coordinate heavy metal ions. The N-alkylaminopyrazole functionalized Au NRs have been characterized by electron microscopy and spectroscopic investigation and tested in optical detection experiments of different ions, namely, Zn(2+), Cd(2+), Hg(2+), Cu(2+), Pb(2+), and As(3+). In particular, the exposure of the functionalized NRs to increasing amounts of Hg(2+) ions has resulted in a gradual red-shift and broadening of the longitudinal plasmon band, up to 900 nm. Interestingly, a significantly different response has been recorded for the other tested ions. In fact, no significant shift in the longitudinal plasmon band has been observed for any of them, while a nearly linear reduction in the plasmon band intensity versus ion concentration in solution has been detected. The very high sensitivity for Hg(2+) with respect to other investigated ions, with a limit of detection of 3 ppt, demonstrates that the functionalization of Au NRs with PyL is a very effective method to be implemented in a reliable colorimetric sensing device, able to push further down the detection limit achieved by applying similar strategies to spherical Au NPs.

Design of new N,O hybrid pyrazole derived ligands and their use as stabilizers for the synthesis of Pd nanoparticles.

We describe the stabilization studies of new palladium nanoparticles (Pd NPs) with a family of hybrid ligands. For this purpose, two new N,O-hybrid pyrazole derived ligands, as well as other previously reported, have been used as NP stabilizing agents following an organometallic approach. A comparison with corresponding palladium complexes has been carried out. We have also studied the superstructures formed by the agglomeration of NPs. To evaluate the scope of the system, different parameters have been studied such as the structure of the ligand, the ligand/metal ratio, the nature of the solvent, the concentration and the reaction time. The colloidal materials resulting from the different syntheses were all characterized by IR, transmission electron microscopy techniques at low or high resolution (TEM and HR-TEM), and scanning electron microscopy (SEM-FEG). All these observations have allowed us to better understand the coordination modes of the different ligands onto the surface of the NPs.

Aminopyrazole-based ligand induces gold nanoparticle formation and remains available for heavy metal ions sensing. A simple "mix and detect" approach.

A novel way to synthesize gold nanoparticles based on the use of N-alkylaminopyrazole is shown. This ligand has a triple functionality: induces AuNPs formation, stabilizes the formed nanoparticles, and even remains available for an external coordination with heavy metal ions. The availability of N-alkylaminopyrazole ligands onto the AuNPs surface is studied using UV-vis and NMR techniques. The mechanism of formation of AuNPs along with the synthesis optimization and characterization are studied using voltammetry and UV-vis, and the results are discussed in detail. The application of N-alkylaminopyrazole-derived gold nanoparticles in the heavy metal ions sensing is also tested showing a high sensitivity for mercury detection at low concentration level. The functionalization of metal nanoparticles with these receptors followed by heavy metal ions detection represents a simple "mix and detect" approach with interest for several other sensing applications.

Variable coordination behavior of new hybrid pyrazole ligand: synthesis and characterization of several Zn(II), Cd(II), Hg(II), Pd(II), Pt(II), and Ni(II) complexes.

In this paper we describe the synthesis of the new mixed-donor ligand 1,8-bis(3,5-dimethyl-1H-pyrazol-1-yl)-3,6-dioxaoctane (L). The complexes [MCl(2)(L)] (M = Zn(II) (1), Cd(II) (2), Hg(II) (3), Pd(II) (4), Pt(II) (6), Ni(II) (7)) and [PdCl(2)(L)](2) (5) were prepared and fully characterized. X-ray crystal structures of complexes 1, 2, 4, 6, and 7 have been determined. The L ligand behaves either as a NN-bidentate (chelate or bridge) and NOON-tetradentate (equatorial or planar) ligand. In these structures, C-H...X (X = O, N or Cl/Cl(-)) intermolecular interactions have been identified and studied. Moreover, the (113)Cd{(1)H}, (195)Pt{(1)H}, and (199)Hg{(1)H} NMR spectra were measured to investigate the coordination environment of the metal in solution. Diffusion NMR studies have also been performed to characterize monomeric and dimeric species of Pd(II). Finally, we have observed that the dimeric complex 5 is converted into the corresponding monomeric complex 4.