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The fundamental implications that chirality has in science and technology require continuous efforts for the development of fast, economic, and reliable quantitative methods for enantiopurity assessment. Among the different analytical approaches, chiroptical techniques in combination with supramolecular methodologies have shown promising results in terms of both costs and time analysis. In this article, a tris(2-pyridylmethyl)amines (

Interest in the catalytic activation of peroxides, together with the requirement of stereoselectivity for the production of enantiopure sulfoxides, has made sulfoxidation the ideal playground for theoretical and experimental physical organic chemists investigating oxidation reactivity. Efforts have been dedicated for elucidating the catalytic pathway regarding these species and for dissecting out the dominant factors influencing the yield and stereochemistry. In this article, Ti(IV) and Hf(IV) aminotriphenolate complexes have been prepared and investigated as catalysts in the presence of peroxides in sulfide oxidation. Experimental results have been combined with theoretical calculations obtaining detailed mechanistic information on oxygen transfer processes. The study revealed that steric issues are mainly responsible for the formation of intermediates in the oxidation pathway. In particular, we could highlight the occurrence of a blended situation where the steric effects of sulfides, ligands, and oxidants influence the formation of different intermediates and reaction pathways.

Fluorescence detected circular dichroism (FDCD) has been used to determine e.e. of carboxylic acids at sensor concentrations down to 0.1 μM also in the presence of chiroptical active contaminants.

The concept of nucleophilicity is at the basis of most transformations in chemistry. Understanding and predicting the relative reactivity of different nucleophiles is therefore of paramount importance. Mayr's nucleophilicity scale likely represents the most complete collection of reactivity data, which currently includes over 1200 nucleophiles. Several attempts have been made to theoretically predict Mayr's nucleophilicity parameters N based on calculation of molecular properties, but a general model accounting for different classes of nucleophiles could not be obtained so far. We herein show that multivariate linear regression analysis is a suitable tool for obtaining a simple model predicting N for virtually any class of nucleophiles in different solvents for a set of 341 data points. The key descriptors of the model were found to account for the proton affinity, solvation energies, and sterics.

Intermolecular interactions sensitive to chirality occur in many biological events. We report a complex formation between a versatile vanadium-based probe and a chiral co-ligand monitored via the combination of electronic circular dichroism (ECD) and Raman scattering. This “ECD-Raman” effect was discovered relatively recently and can be measured using a Raman optical activity (ROA) spectrometer. Simulated spectra based on experimental ECD and degree of circularity (DOC) values agree with the observed ones. Sensitive recognition of the chiral enantiopure co-ligand is thus enabled by a combination of resonance of the excitation light with the diastereoisomeric complex, co-ligand complexation, circular dichroism, and polarized Raman scattering from the achiral solvent. Relatively dilute solutions could be detected (10−4 mol dm−3), about 1000× less than is necessary for conventional ROA detection of the pure co-ligand and comparable to concentrations needed for conventional ECD spectroscopy. The results thus show that differential ECD-Raman measurements can be conveniently used to monitor molecular interactions and molecular spectroscopic properties.

The spin–spin interactions between unpaired electrons in organic (poly)radicals, especially nitroxides, are largely investigated and are of crucial importance for their applications in areas such as organic magnetism, molecular charge transfer, or multiple spin labeling in structural biology. Recently, 2,2,6,6-tetramethylpiperidinyloxyl and polymers functionalized with nitroxides have been described as successful redox mediators in several electrochemical applications; however, the study of spin–spin interaction effect in such an area is absent. This communication reports the preparation of a novel family of discrete polynitroxide molecules, with the same number of radical units but different arrangements to study the effect of intramolecular spin–spin interactions on their electrochemical potential and their use as oxidation redox mediators in a Li–oxygen battery. We find that the intensity of interactions, as measured by the d1/d electron paramagnetic resonance parameter, progressively lowers the reduction potential. This allows us to tune the charging potential of the battery, optimizing its energy efficiency., This work was supported by: DGICT-MINECO (MAT2016-80826-R, MAT2017-91404-EXP, RTI2018-09273-B-I00), AGAUR (2017 SGR 918, 2014 SGR 1505, 2017 SGR 1687) and University of Padova. ICMAB acknowledges Spanish MINECO through the Severo Ochoa Centres of Excellence Programme Grant SEV- 2015-0496 and S.Z. his CSC grant.

The direct α-arylation of carbonyl compounds emerged over the last two decades as a straightforward method for the formation of C(sp3)–C(sp2) bonds. Mechanistic studies suggested a classical cross-coupling catalytic cycle. This consists of oxidative addition of the aryl halide (ArX) to the Pd(0)-catalyst, transmetallation of the Na- or K-enolate generated in situ, and subsequent reductive elimination. Even though the general reaction mechanism was thoroughly investigated, studies focusing on enantioselective variants of this transformation are rare. Here, the computational study of the [Pd(BINAP)]-catalyzed α-arylation of 2-methyltetralone with bromobenzene is reported. The whole reaction energy profile was computed and several mechanistic scenarios were investigated for the key steps of the reaction, which are the enolate transmetallation and the C–C bond-forming reductive elimination. Among the computed mechanisms, the reductive elimination from the C-bound enolate Pd complex was found to be the most favorable one, providing a good match with the stereoselectivity observed experimentally with different ligands and substrates. Detailed analysis of the stereodetermining transition structures allowed us to establish the origin of the reaction enantioselectivity.

Aromatic stacking interactions have been a matter of study and debate due to their crucial role in chemical and biological systems. The strong dependence on orientation and solvent together with the relatively small interaction energies have made evaluation and rationalization a challenge for experimental and theoretical chemists. We have used a supramolecular cage formed by two tris(pyridylmethyl)amines units to build chemical Double Mutant Cycles (DMC) for the experimental measurement of the free energies of π‐stacking interactions. Extrapolating the substituent effects to remove the contribution due to electrostatic interactions reveals that there is a substantial contribution to the measured stacking interaction energies which is due to non‐polar interactions (−3 to −6 kJ mol−1). The perfectly flat nature of the surface of an aromatic ring gives π‐stacking an inherent advantage over non‐polar interactions with alkyl groups and accounts for the wide‐spread prevalence of stacking interactions in Nature., A double‐Hammett approach has been used to dissect out the polar contributions to the total aromatic stacking energy.

The generation of hydrogen from water represents an important task towards a carbon neutral economy. Within this context, the preparation of hybrid electrodes merging the versatility of solid-state porous substrates and the catalytic ability and tunability of molecular complexes represents a great challenge. In the present work, we report on the preparation of hybrid cathodes for the hydrogen evolution reaction (HER) through an unprecedented combination of single-walled carbon nanohorns (SWCNHs) and two novel cobalt(II) polypyridine complexes based on the tris(2-pyridylmethyl)amine (TPMA) ligand scaffold. Suitable pyrene groups are introduced in the ligand framework in different positions to provide a way for direct anchoring onto the carbonaceous substrate by exploiting non-covalent π–π interactions. The present systems behave as competent cathodes for the HER in neutral aqueous solution with overpotentials of η ∼ 0.5 V and stable current densities (within 1 h electrolysis) up to −0.50 mA cm−2, whose exact values depend on the catalyst used and are mainly related to the respective loading on the electrode surface. In both cases, hydrogen evolution is detected under continuous electrolysis for up to ca. 12 h leading to maximum turnover numbers (TONs) of 4700 and 9180 molH2 molCo−1 for the two different complexes. The progressive deactivation under electrolytic conditions is mainly ascribed to leaching of the metal centre from the polydentate ligand, likely occurring from the competent catalytic intermediates involved in the HER.

A novel catalytic system based on copper(I) and chiral bis(phosphine) dioxides is described. This allows the arylation of silyl enol ethers to access enolizable α-arylated ketones in good yields and enantiomeric excess up to 95%. Noncyclic ketones are amenable substrates with this method, which complements other approaches based on palladium catalysis. Optimization of the ligand structure is accomplished via rational design driven by correlation analysis. Preliminary mechanistic hypotheses are also evaluated in order to identify the role of chiral bis(phosphine) dioxides.

Three gold(I) tripodal complexes containing the tris(2-pyridylmethyl)amine (TPA) ligand coordinated to Au–PR3 moieties (PR3 = 1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane, PTA (1), 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane, DAPTA (2) and triphenylphosphane (3)) were prepared together with a cage-like structure containing triphosphane 1,1,1-tris(diphenylphosphinomethyl)ethane (4). The luminescence of these complexes has been studied and they show a red shift upon the formation of heterometallic complexes by reaction with Zn(NO3)2, CuCl and [Cu(CH3CN)4]BF4. The different coordination motifs of the Zn2+ and Cu+ heterometallic species and the resulting changes in the recorded absorption, emission and NMR spectra were analysed and supported by TD-DFT calculations.

The chance to have persistent organic radicals in combination with metals has attracted much interest since it offers the possibility of having new functional molecules with multiple open-shell elements. In this study, we report the synthesis of two tripodal tris(2-pyridyl)methylamine ligands (TPMA) functionalized with nitronyl nitroxide persistent radicals. The newly formed ligands have been used to coordinate zinc(II), copper(II), iron(II) and cobalt(II). The resulting complexes have been investigated by means of electron paramagnetic resonance (EPR), ESI-MS, FT-IR spectroscopy and X-ray diffraction. An electron reduction of the N–O radical moiety has been observed, depending on the metal used for the formation of the complex and the reaction conditions. We have observed small differences in the EPR spectra depending on the meta or para position of the radical moiety in the complex structure and some antiferromagnetic interactions between the paramagnetic M(II) ions and the radical species., This work was supported by DGICT-MINECO (MAT2016-80826-R) and AGAUR (2017 SGR 918). ICMAB acknowledges Spanish MINECO for the Severo Ochoa Centres of Excellence Programme Grant SEV-2015-0496.

Enantiomeric excess (ee) determination is crucial in many aspects of science, from synthesis to materials. Within this subject, coupling molecular sensors with chiroptical techniques is a straightforward approach to the stereochemical analysis of chiral molecules, especially in terms of process immediacy and labor. Stereodynamic probes typically consist of racemic mixtures of rapidly interconverting enantiomeric conformers able to recognize a chiral analyte and greatly amplify its chiroptical readout. A great number of sensors have been developed, but their activity is generally restricted to one or a few classes of chemicals, and the analysis outcome relies on precise knowledge of the probe and analyte concentrations. This aspect in particular limits the potential practical applications. Here we report an oxo-vanadium(V) aminotriphenolate complex that was found to act as a concentration-independent stereodynamic sensor for a wide range of compounds. The bare complex is CD-silent, but coordination of an enantioenriched substrate immediately gives rise to intense Cotton effects in the visible region. Furthermore, a geometry change during the substrate-complex interaction leads to a marked optical response, as witnessed by a strong red-shift of the probe absorption bands, thus allowing the generation of dichroic signals in an "interference-free" area of the spectrum. This peculiarity allows for a linear correlation at high wavelengths between the ee of the analyte and anisotropy g-factor. This parameter derives from the differential circularly polarized light absorption of the sample but is independent of concentration. The newly developed sensor based on a simple coordination process has an unprecedented general character in terms of substrate scope and employment.

The widespread presence of aromatic stacking interactions in chemical and biological systems, combined with their relatively small energetic contribution, have led to a plethora of theoretical and experimental studies for their quantification and rationalization. Typically, π–π aromatic interactions are studied as a function of substituents to gather information about the interaction mechanism. While experiments suggest that aromatic interactions are dominated by local electrostatic contacts between π-electron density and CH groups, theoretical work has raised the possibility that direct electrostatic interactions between local dipoles of the substituents may play a role. We describe a supramolecular cage that binds two aromatic carboxylates in a stacked geometry such that the aromatic substituents are remote in space. Chemical Double Mutant Cycles (DMCs) were used to measure fifteen different aromatic stacking interactions as a function of substituent (NMe2, OMe, Me, Cl and NO2). When both aromatic rings have electron-withdrawing nitro substituents, the interaction is attractive (−2.8 kJ mol−1) due to reduced π-electron repulsion. When both aromatic rings have electron-donating di-methylamino substituents, the interaction is repulsive (+2.0 kJ mol−1) due to increased π-electron repulsion. The results show that aromatic stacking interactions are dominated by short range electrostatic contacts rather than substituent dipole interactions.

Self-assembly of a modified tris(2-pyridylmethyl)amine TPMA ligand, zinc(II) or cobalt(II) ions, and amino acids have been used effectively as stereo dynamic optical probes for the determination of the enantiomeric excess of free amino acids either using Electronic or Vibrational Circular Dichroism (CD and VCD). Herein, we report the mechanistic and stereochemical study of the self-assembly process which reveals a complex equilibrium in solution where even small variations in the experimental conditions can profoundly affect the final products of the reaction. In particular, variation on the metal stoichiometry switch give rises to an entirely enantio narcissistic self-assembly of the structure.

Confined molecular environments have peculiar characteristics that make their properties unique in the field of biological and chemical sciences. In recent years, advances in supramolecular capsule and cage synthesis have presented the possibility to interpret the principles behind their self‐assembly and functions, which has led to new molecular systems that display outstanding properties in molecular recognition and catalysis. Herein, we report a rapid method based on ESI‐MS to determine the binding profiles for linear saturated dicarboxylic acids in a series of different cages. The cages were obtained by self‐assembly of modified tris(pyridylmethyl)amine (TPMA) complexes and diamines chosen to explore variations in their size and flexibility. This methodology has provided information on how small changes in the structures of the host and guest can contribute to recognition events. Moreover, it was possible to study molecular systems that contain paramagnetic metals, which are not suitable for classical binding‐constant determination by 1H NMR spectroscopy. peerReviewed

Novel cobalt, nickel, and iron complexes based on the pentadentate 8-hydroxyquinoline-di(2-picolyl)amine ligand were synthesized and thoroughly characterized. X-ray structures of both the cobalt and iron complexes were also obtained, showing the tendency to adopt a pseudo-octahedral geometry by coordination of an additional sixth ligand. These metal complexes were then studied as potential hydrogen-evolving catalysts (HECs) under both electrochemical and light-driven conditions. In particular, two different photochemical systems were tested involving either Ru(bpy)32+/ascorbic acid or Ir(ppy)2(bpy)+/TEA sensitizer/sacrificial donor couples. The electrochemical results showed that these metal complexes may behave as competent HECs. However, under photochemical conditions, only the cobalt compound displayed substantial hydrogen-evolving activity in both ruthenium- and iridium-based systems. The nickel and iron complexes, on the other hand, exhibited appreciable photocatalytic activity only in the iridium-based photochemical system, while showing negligible hydrogen evolution ability when employed in the ruthenium-based one.

A novel supramolecular cage built from the self-assembly of tris(2-pyridylmethyl)amine zinc complexes through imine condensation chemistry is reported. The cage recognition properties over a variety of structurally related guests, together with the kinetic study of the template assembly and disassembly, have been investigated in detail. This knowledge has been used to selectively modulate the rate of both assembly and disassembly processes. In particular, a novel disassembly method induced by strain release of the guest has been developed.

Vanadium(V) complexes derived from aminotriphenolate ligands are demonstrated to be highly active catalysts for the coupling of various terminal and internal epoxides with carbon dioxide to afford a series of substituted organic carbonates in good yields. Intriguingly, a V(V) complex bearing peripheral chloride groups on the ligand framework allowed for the formation and isolation of a rare complex that incorporates a ring-opened epoxide with one of the phenolateO atoms acting as a nucleophile and the metal center as a Lewis acidic site. This unusual structure was characterized by X-ray diffraction and 51V-NMR, and was shown to exhibit catalytic activity for the coupling of propylene oxide and CO2 when combined post-synthetically with these substrates. The results obtained herein clearly show that vanadium complexes in a high oxidation state are powerful catalysts for the activation of challenging internal epoxides, and their conversion into cyclic organic carbonates.

The activation of small molecules has become an increasingly popular area of research over the last years, and there are many reasons to be captivated by this fascinating topic.

Amino triphenolate tungsten(VI) complexes have been prepared and they proved to be efficient catalysts in haloperoxidation reactions using hydrogen peroxide as a terminal oxidant and inorganic sources of halides. In particular, interesting results have been obtained in the challenging chloroperoxidation reactivity (catalyst loading down to 0.05% with TONs up to 900). A comparison among three different metal complexes bearing the same ligand (vanadium(V), molybdenum(VI) and tungsten(VI)) showed much better performances of the last complex both on bromo and chloro peroxidations., Universita di Padova [PRAT-CPDA123307, CPDA153122]; MIUR (PRIN) [2010CX2TLM_002]; TUBITAK [113Z414]; Universita di Padova (Attrezzature Scientifiche Finalizzate alla Ricerca), This research was supported by: Universita di Padova (PRAT-CPDA123307, CPDA153122, and Attrezzature Scientifiche Finalizzate alla Ricerca 2014), MIUR (PRIN-2010-11 2010CX2TLM_002 E. B Fellowship) and it has been carried out in the frame of COST Action CM1205 Catalytic Routines for Small Molecules Activation (CARISMA). AD also thanks TUBITAK (113Z414) for supporting the project.

We designed a stereodynamic system, where the chirality of the analyte serves as a template for the helicity of the first coordination sphere of Co(ii). Giant VCD bands induced by Co(ii) allow the measurement of a completely significant and conclusive VCD spectrum in only a few seconds and/or on minute quantities of the analyte. This paves the way for the development of similar protocols, overcoming the limitations due to weak VCD signals for the assignment of absolute configurations.

Vanadium complexes have proven to be effective catalysts for the activation of peroxides and the selective oxidation of substrates like bromides, sulfides and alkenes. Besides their capability to form metalloperoxo species, which effectively transfer oxygen atoms to the substrate, these systems are synthetically useful for obtaining valuable oxidized molecules on a preparative scale, with a high degree of selectivity and TONs. Furthermore, the use of environmentally friendly oxidants like hydrogen and alkyl hydroperoxides increases significantly their potential application at an industrial level. Here we report a critical survey on the most effective homogeneous vanadium catalysts reported in the last decade concerning their synthetic application in oxygen transfer reactions (sulfoxidation, epoxidation, haloperoxidation) using hydrogen peroxide or alkyl hydroperoxides, demonstrating the different classes of ligands and complexes, their catalytic performances, their reactivity, chemo, stereo and substrate selectivity. Some examples of the use of non conventional reaction media or techniques and catalyst recycling studies will be also discussed.

The enhancement of the reactivity of peroxides, particularly hydrogen peroxide and alkylhydroperoxides, in the presence of vanadium catalysis is a very well known process. The catalytic effect is determined by the formation of an intermediate whose nature depends on the peroxides used and on its interaction with the metal precursor, high-valent peroxo vanadium species being usually the reactive oxidants. During the last decades the mechanistic details for several types of oxidation reactions have been elucidated. Interestingly, in a number of cases theoretical calculations offered support to the proposed reaction pathways. In general, V(V) peroxo species behave as electrophilic oxygen transfer reagents thus reacting preferentially with the more nucleophilic functional group present in the molecule. In several instances the chemoselectivity observed in such processes is very high when not absolute. As far as vanadium peroxides are concerned, a radical oxidative reactivity toward alkanes and aromatics has been also observed; also for this latter chemistry, diverse research groups studied in detail the mechanism. On the other hand, no clear-cut evidence of nucleophilic reactivity of vanadium peroxo complexes has been obtained. Here we collect a selection of recent achievements concerning the reaction mechanisms in the vanadium catalysed oxidation and bromination reactions with peroxides.

Homochiral trialkanolamines are a new class of chiral ligand for enantioselective catalysis. Mononuclear titanium complexes bearing such ligands promote the asymmetric sulfoxidation of alkyl aryl sulfides. In contrast, a dimeric zirconium species is the active catalyst in the desymmetrization of meso epoxides with azides. Mechanistic insight into the latter reaction has led to a new reaction, the enantioselective desymmetrization of meso epoxides using halides as the nucleophilic partner. HOMOCHIRAL TRIALKANOLAMINES Several years ago (ref. 1) we introduced homochiral trialkanolamines 1 as ligands for enantioselective catalysts based on early transition metals. These ligands have several advantages. They are easy to synthesize; many enantiopure epoxides react directly with ammonia according to eq. 1: H%R 60 deg C MeOH OH QH NH3 + 3 R 1 A Moreover, ligands 1 bind tightly to early transition metals in a tetradentate fashion to form robust complexes which persist even in the presence of water or silylating agents. The three asymmetric centers provide a highly asymmetric environment in coordination sphere of the transition metal. Ligands 1 displace monodentate alkoxides from group 4-6 metal alkoxides to provide the corresponding trialkanolamine(3-) complexes. An example is the reaction of homochiral triisopropanolamine with titanium(1V) isopropoxide shown in eq. 2: TH F AcCl OH Ti(OiPr)4 + N A ,LTiOiPr LTiCl (2) iPrOAc \/.a 3 iPrOH Treatment of the resultant LTiOiPr with acetyl chloride affords the LTiCl complex, 2. The x-ray crystal structure of 2 is shown in Figure 1. It can be seen that the ligand adopts a highly symmetrical C3 stereochemistry and provides a complex whose shape could be described as a “rotor” or “pinwheel”.

This research was supported by the Universita di Padova, Italy(grant numbers PRAT-CPDA123307 and CPDA153122, Attrezza-ture Scientifiche Finalizzate Alla Ricerca 2014) and the ItalianMinistero dell'Universita e della Ricerca (MIUR) (PRIN-2010-112010CX2TLM_002, E. B. fellowship). This work was carried outwithib the framework of the COST Action CM1205, CatalyticRoutines for Small Molecules Activation (CARISMA). The SpanishDireccion General de Investigacion (BeWell Grant numberCTQ2013-40480-R) and L'Agencia de G estio d'Ajuts Universitarisi de Recerca (AGAUR) (grant number 2014-SGR-17) are also ac-knowledged. CIBER-BBN is an initiative funded by the VI Na-tional R&D&i Plan 2008–2011, Iniciativa Ingenio 2010, Consol-ider Program, CIBER Actions and financed by the Instituto deSalud Carlos III with assistance from the European Regional De-velopment Fund.

The C 3 vanadium(V) amine triphenolate complex 1f has been characterized as a structural and functional model of vanadium haloperoxidases. The complex catalyzes efficiently sulfoxidations at room temperature using hydrogen peroxide as the terminal oxidant, yielding the corresponding sulfoxides in quantitative yields and high selectivities (catalyst loading down to 0.01%, TONs up to 9900, and TOFs up to 8000 h (-1)) as well as bromination of 1,3,5-trimethoxybenzene (catalyst loading down to 0.05%, TONs up to 1260, and TOFs up to 220 h (-1)).

A novel, mononuclear Ti(IV) amine triphenolate complex obtained by reaction of Ti(OiPr)(4) with tris(2-hydroxy-3-phenylbenzyl)amine bearing phenyl ortho-substituents affords quantitatively and spontaneously the corresponding heterochiral micro-oxo dinuclear compound whereas an analogous chiral, enantiopure complex maintains its mononuclear structure even in the presence of an excess of water.

An efficient procedure for highly chemo- and stereoselective cyclization of (S)-allylalanine derivatives is reported (diastereomeric ratios up to 96:4) where the reaction course can be completely controlled by switching from gamma-lactones to cyclic carbamates simply with the proper choice of the amino acid protecting groups. Both processes are stereoconvergent and afford the (S,S)-products in high yields, short reaction times, and mild reaction conditions.

CARISMA is a currently running COST Action that pools leading European experts in computational and experimental chemistry to foster synergies for developing new catalytic processes for the transformation of abundant small molecules such as water, carbon dioxide, or ammonia into high-value chemicals and energy-relevant products. CARISMA promotes new collaborations, exchange of knowledge and skills, frontier training to young as well as established researchers, and a platform for the advancement of theoretical and experimental research in an iterative process, comprised of expertise in various connate domains including synthesis, catalysis, spectroscopy, kinetics, and computational chemistry. These interactions stimulate the discovery of new and efficient catalytic processes, illustrated in the second part of this contribution with the collaborative development of powerful iridium-based complexes for bond activation and water oxidation catalysis.

Monomeric Ti(IV)/C3 trialkanolamine complexes are effective catalysts in the stereoselective sulfoxidation of alkyl aryl sulfides (ee's up to 84%, 0.1% of catalyst). Such complexes were shown to have a biphilic nature, behaving as electrophilic oxidants towards sulfides while a nucleophilic pathway dominates the oxidation of sulfoxides. The analogous Zr(IV) complexes, likely dimeric, are even better and more general stereoselective sulfoxida- tion catalysts (ee's up to 91%, 50 T.O.), affording sulfoxides with the opposite absolute configuration.

A series of tris(2-aminoethyl)amine (TREN) derivatives functionalized on the arms with pyridine or methylimidazole ligands bind very strongly to a trisporphyrin derivative via apical coordination, with formation of molecular cages; the strength of the binding (Kb up to 108.8 mol−1 dm3) depends on the structure of the TREN derivative as well as on its coordination to Zn(II).