Mononuclear or Coordination Polymer Complexes? Both Are Possible for 3,6,9-Trioxaundecanedioic Acid.

Investigating the driving forces leading to the formation of a specific supramolecular architecture among a wide spectrum of all the possibly obtainable structures is not an easy task. The contemporary literature provides several models for correctly predicting the thermodynamically accessible structures that can originate from a library of building blocks. Definitions are rigid by their very nature, so their application may sometimes require a shift in perspective. In the study presented herein, we describe the crystal structures of three metallo-supramolecular architectures assembled from deprotonated derivatives of 3,6,9-trioxaundecanedioic acid and Mn(II), Co(II) and Zn(II). In the Mn(II) case, the complexation resulted in a complex of a discrete/heptacoordinated nature, whereas the other two structures appeared as helical polymers. To explain such an anomaly, in this work, we describe how the interplay between the flexibility of the ligand spacer and the number of coordinating atoms involved determines the divergent or convergent organisation of the final coordination architecture.

Which DFT factors influence the accuracy of 1H, 13C and 195Pt NMR chemical shift predictions in organopolymetallic square-planar complexes? New scaling parameters for homo- and hetero-multimetallic compounds and their direct applications.

Because of their chemical heterogeneity, stereochemical complexity and the presence of heavy atoms involving orbitals with high quantum number L, organopolymetallic complexes require considerable focus during their NMR spectral interpretation. Until now, computational NMR studies have mainly focused on mono-nuclear species; at the same time, recent literature displays that new synthetic procedures are being developed to efficiently insert two or more metals into organic scaffolds, and hence an ad hoc theoretical NMR protocol is urgently required. This study, exploiting a solid calibration set, provides a comprehensive overview of the 1H, 13C and 195Pt NMR prediction trends when DFT parameters are scanned. The best performing levels for 1H (GIAO/TPSSTPSS/x2c-TZVPPallS/SUPERFINE/SMD), 13C (GIAO/CAM-B3LYP/Jorge-TZP/SUPERFINE/CPMC) and 195Pt (GIAO/TPSSTPSS/LANL2DZ/SUPERFINE/SMD) were employed as guidance for important NMR elucidations including both regio- and stereo-chemical features. Finally, the presented fitted scaling factors were proved to have a considerable transferibility between different solvents without re-parameterization.

Photoinduced Electron Transfer in Organized Assemblies-Case Studies.

In this review, photoinduced electron transfer processes in specifically designed assembled architectures have been discussed in the light of recent results reported from our laboratories. A convenient and useful way to study these systems is described to understand the rules that drive a light-induced charge-separated states and its subsequent decay to the ground state, also with the aim of offering a tutorial for young researchers. Assembled systems of covalent or supramolecular nature have been presented, and some functional multicomponent systems for the conversion of light energy into chemical energy have been discussed.

Intermolecular Forces Driving Hexamethylenetetramine Co-Crystal Formation, a DFT and XRD Analysis.

Interest in co-crystals formation has been constantly growing since their discovery, almost a century ago. Such success is due to the ability to tune the physical-chemical properties of the components in solid state by avoiding a change in their molecular structure. The properties influenced by the co-crystals formation range from an improvement of mechanical features and chemical stability to different solubility. In the scientific research area, the pharmacological field is undoubtedly one of those in which an expansion of the co-crystal knowledge can offer wide benefits. In this work, we described the crystalline structure of hexamethylenetetramine co-crystallized with the isophthalic acid, and we compared it with another co-crystal, showing the same components but different stoichiometry. To give a wider overview on the nature of the interactions behind the observed crystal packing and to rationalize the reasons of its formation, a computational analysis on such structures was carried out.

Supramolecular BODIPY based dimers: synthesis, computational and spectroscopic studies.

The synthetic procedures for the preparation of supramolecular BODIPY dimers decorated with complementary patterns able to induce the formation of a triple hydrogen bond through mutual interactions are here reported. The BODIPY and styryl-equipped BODIPY species have been suitably functionalized in meso position with 2,6-diacetamido-4-pyridyl and 1-butyl-6-uracyl moieties. Dimers and monomers have been subjected to computational and photophysical investigations in solvent media. Various peculiarities concerning the effects of the interaction geometry on the stability of the H-bonded systems have also been investigated. The combination of modelling and experimental data provides a paradigm for improving and refining the BODIPY synthetic pathway to have chromophoric architectures with a programmable supramolecular identity. Furthermore, the possibility of assembling dimers of different dyes through H-bonds could be appealing for a systematic investigation of the principal factors affecting the dynamics of the energy migration and possibly driving coherent transfer mechanisms. Our work highlights how the chemical versatility of these dyes can be exploited to design new BODIPY-based supramolecular architectures.

The effect of hydrogen bonds on the ultrafast relaxation dynamics of a BODIPY dimer.

The influence of hydrogen bonds (H-bonds) in the structure, dynamics, and functionality of biological and artificial complex systems is the subject of intense investigation. In this broad context, particular attention has recently been focused on the ultrafast H-bond dependent dynamical properties in the electronic excited state because of their potentially dramatic consequences on the mechanism, dynamics, and efficiency of photochemical reactions and photophysical processes of crucial importance for life and technology. Excited-state H-bond dynamics generally occur on ultrafast time scales of hundreds of femtoseconds or less, making the characterization of associated mechanisms particularly challenging with conventional time-resolved techniques. Here, 2D electronic spectroscopy is exploited to shed light on this still largely unexplored dynamic mechanism. An H-bonded molecular dimer prepared by self-assembly of two boron-dipyrromethene dyes has been specifically designed and synthesized for this aim. The obtained results confirm that upon formation of H-bonds and the dimer, a new ultrafast relaxation channel is activated in the ultrafast dynamics, mediated by the vibrational motions of the hydrogen donor and acceptor groups. This relaxation channel also involves, beyond intra-molecular relaxations, an inter-molecular transfer process. This is particularly significant considering the long distance between the centers of mass of the two molecules. These findings suggest that the design of H-bonded structures is a particularly powerful tool to drive the ultrafast dynamics in complex materials.

Do Secondary Electrostatic Interactions Influence Multiple Dihydrogen Bonds? AA-DD Array on an Amine-Borane Aza-Coronand: Theoretical Studies and Synthesis.

Hydrogen bond plays a key role in a wide range of inorganic, organic, as well as biological systems. The understanding on how the chemical environment can affect this kind of interaction is crucial to predict its binding strength and consequently the robustness and the dynamic properties of many supramolecular systems. In this paper a new donor-acceptor complex was synthesized and characterized by SCXRD, showing for the first time in an organic system an AA-DD pattern of a particular hydrogen interaction, called dihydrogen bond. Over 250 functionals were computationally evaluated to select the best method to reproduce the binding interaction geometry of this new pattern. Moreover, a new vector force model was used to split the contribution of primary and secondary electrostatic interactions (SEIs), in order to evaluate how the latter one can modify the binding strength of this unusual hydrogen-hydrogen interaction.

Fast transport of HCl across a hydrophobic layer over macroscopic distances by using a Pt(II) compound as the transporter: micro- and nanometric aggregates as effective transporters.

Bis-(diethyl-dithioxamidate)platinum(ii) is able to transport HCl from the donor aqueous phase to the receiving one over a mean distance of 12 cm in about 3 minutes across an organic membrane in the bulk, without stirring of the organic phase, i.e. at a rate far exceeding the unidirectional macroscopic diffusion coefficient. The way in which this surprising phenomenon can happen is linked to the behaviour of HCl which, because of dynamic interactions with [Pt(HEt2C2N2S2)2] (in which HCl is hosted as a tight ion pair [Pt(H2Et2C2N2S2)2][Cl]2) and chloroform molecules, gives rise to observable nanometric and micrometric domains, more dense than the surrounding bulk, whose formation and disaggregation processes accelerate the unidirectional macroscopic diffusion of HCl. Thermodynamic parameters obtained from the study of acid-base behaviour of the system Pt(ii) species/HCl/CHCl3 also agree with the proposed mechanism of HCl transport.

Theoretical prediction of 13C NMR spectrum of mixed triglycerides by mean of GIAO calculations to improve vegetable oils analysis.

This pioneering study based on GIAO-DFT methods is aimed to the best prediction of 13C Nuclear Magnetic Resonances (NMR) arising from triglycerides (and also glycerols), known to be the main component of vegetable oils. Provided that fatty esters bound to the glycerol moiety are not affected by the other esterification chains, and slightly affected by their own esterification position (2- internal, or 1/3- external), eight natural molecules are first optimized despite the challenging presence of many non-hydrogen atoms and the large conformational freedom. This preliminary study sheds light on the total chemical shift prediction concerning five fatty esters (Oleic, Palmitic, Linoleic, Stearic and Linolenic) either present in internal or external positions (ten fragments in total); these results display a very good matching to the experimental profile recorded for several vegetable oils chosen as natural mixtures of glycerides. In order to further improve the theoretical to experimental matching, ten simplified triglycerides with the mentioned fatty esters in the two different esterification positions, and flanked by acetyl esters, were studied and optimized. Beyond the best matching reached so far, we notice that the theoretical rationalisation of the overcrowding in the 28.7-29 ppm spectral region in unable to decode the necessary resolution, nonetheless the same theoretical prediction can still drive the appropriate assignments (as for the fifth and sixth carbon attribution of every chain) even against actual misleading reports.

Development of Polymeric Membranes Based on Quaternized Polysulfones for AMFC Applications.

A series of quaternary ammonium-functionalized polysulfones were successfully synthesized using a chloromethylation two-step method. In particular, triethylammonium and trimethylammonium polysulfone derivatives with different functionalization degrees from 60% to 150% were investigated. NMR spectroscopic techniques were used to determine the degree of functionalization of the polymers. The possibility to predict the functionalization degree by a reaction tool based on a linear regression was highlighted. Anionic membranes with a good homogeneity of thickness were prepared using a doctor-blade casting method of functionalized polymers. The chemical-physical data showed that ion exchange capacity, water content, and wettability increase with the increase of functionalization degree. A higher wettability was found for membranes prepared by the trimethylamine (TMA) quaternary ammonium group. A degree of functionalization of 100% was chosen for an electrochemical test as the best compromise between chemical-physical properties and mechanical stability. From anionic conductivity measurement a better stability was found for the triethylamine (TEA)-based membrane due to a lower swelling effect. A power density of about 300 mW/cm2 for the TEA-based sample at 60 °C in a H2/O2 fuel cell was found.

Antiproliferative Activities of Diimine-Based Mixed Ligand Copper(II) Complexes.

A series of Cu(diimine)(X-sal)(NO3) complexes, where the diimine is either 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen) and X-sal is a monoanionic halogenated salicylaldehyde (X = Cl, Br, I, or H), have been synthesized and characterized by elemental analysis and X-ray crystallography. Penta-coordinate geometries copper(II) were observed for all cases. The influence of the diimine coligands and different halogen atoms on the antiproliferative activities toward human cancer cell lines have been investigated. All Cu(II) complexes were able to induce a loss of A2780 ovarian carcinoma cell viability, with phen derivatives more active than bpy derivatives. In contrast, no in vitro antiproliferative effects were observed against the HCT116 colorectal cancer cell line. These cytotoxicity differences were not due to a different intracellular concentration of the complexes determined by inductively coupled plasma atomic emission spectroscopy. A small effect of different halogen substituents on the phenolic ring was observed, with X = Cl being the most highly active toward A2780 cells among the phen derivatives, while X = Br presented the lowest IC50 in A2780 cells for bpy analogs. Importantly, no reduction in normal primary fibroblasts cell viability was observed in the presence of bpy derivatives (IC50 > 40 µM). Mechanistically, complex 1 seems to induce a stronger apoptotic response with a higher increase in mitochondrial membrane depolarization and an increased level of intracellular reactive oxygen species (ROS) compared to complex 3. Together, these data and the low IC50 compared to cisplatin in A2780 ovarian carcinoma cell line demonstrate the potential of these bpy derivatives for further in vivo studies.