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Meso-5,10,15,20-tetrakis-3,5-di-tert-butyl-4-oxocyclohexadienylideneporphyrinogen, OxP, is a versatile, highly colored chromophore with strong broad absorption in the visible range. It is derived from meso-5,10,15,20-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin by two-electron oxidation, and the OxP tetrapyrrole moiety exists in a saddle conformation. N-Alkylation of the OxP core nitrogen atoms can be used to functionalize the chromophore leading to a class of stable molecules with highly substituted peripheries. Substituted OxPs can act as singlet oxygen generators under light irradiation and the efficacy of this process is influenced by the multiplicity of N-substitution, and by the chemical identity of those substituents. Bromination of the macrocyclic [Formula: see text]-positions can also be used to control singlet oxygen generation by the relevant derivatives. We report the quantum yields of singlet oxygen generation for a series of differently substituted OxP derivatives whose metrics indicate that these compounds possess significant potential in the corresponding applications including photodynamic therapy, bacterial inactivation therapy, and organic transformations.

A novel fused porphyrinoid undergoes supramolecular assembly to form a persistently porous solution processable material for sensing of acetone vapour under high humidity using a membrane-type surface stress sensor.

Molecular rotors are an important class of dynamic molecules which have been studied not only for their possible uses as components of molecular machines but also because of potential applications as probes of local viscosity in biological media, especially self-assembled membranes. For the former, factors affecting rotational motility are critical while for the latter the rotor activity must be complexed with an output signal (often fluorescence) for reporting of local conditions. Molecular single stator-double rotor activity of an oxidized resorcinarene (fuchsonarene) macrocycle containing unsaturated hemiquinonoid groups at its meso positions was investigated. Fuchsonarenes contain two hemiquinonoid substituents at diagonally-opposed meso-positions with two electron rich phenol groups at the remaining meso-positions between the hemiquinonoid groups. All meso-substituents are in proximity at one side of the resorcinarene macrocycle (so-called rccc-type isomer) with rotational activity of the phenol meso-substituents. Rotation rates of the phenol moieties can be controlled by varying temperature, solvent polarity and acidity of the medium of study with rotation being thermally activated in neutral and acidic media and tunable in the range from 2 s−1 to 20 000 s−1. Experimental and computational data indicate that rotation of the mobile phenol meso-substituents is remotely affected by interactions with acidic solvents at the carbonyl CO groups of macrocyclic acetyloxy groups, which occurs with the emergence of a lower energy electronic absorption band whose intensity is correlated with both the acidity of the medium and the rotation rate of the phenol substituents. Time-dependent DFT calculations suggest that the low energy band is due to a molecular conformational adjustment affecting electronic conjugation caused by strong interaction of macrocyclic acetyloxy carbonyl groups with the acid medium. The work presents a molecular mechanical model for estimating solution acidity and also gives insight into a possible method for modulating rotor activity in molecular machines.

A new type of push–pull charge transfer complex, viz., a spiro-locked N-heterocycle-fused zinc porphyrin, ZnP-SQ, is shown to undergo excited state charge separation, which is enhanced by axial F− binding to the Zn center. In this push–pull design, the spiro-quinone group acts as a ‘lock’ promoting charge transfer interactions by constraining mutual coplanarity of the meso-phenol-substituted electron-rich Zn(ii) porphyrin and an electron deficient N-heterocycle, as revealed by electrochemical and computational studies. Spectroelectrochemical studies have been used to identify the spectra of charge separated states, and charge separation upon photoexcitation of ZnP has been unequivocally established by using transient absorption spectroscopic techniques covering wide spatial and temporal regions. Further, global target analysis of the transient data using GloTarAn software is used to obtain the lifetimes of different photochemical events and reveal that fluoride anion complexation stabilizes the charge separated state to an appreciable extent., A new type of push–pull charge transfer complex, viz., a spiro-locked N-heterocycle-fused zinc porphyrin, ZnP-SQ, is shown to undergo excited state charge separation, which is enhanced by axial F− binding to the Zn center.

Designing fluorescent molecules requires considering multiple interrelated molecular properties, as opposed to properties that straightforwardly correlated with molecular structure, such as light absorption of molecules. In this study, we have used a de novo molecule generator (DNMG) coupled with quantum chemical computation (QC) to develop fluorescent molecules, which are garnering significant attention in various disciplines. Using massive parallel computation (1024 cores, 5 days), the DNMG has produced 3643 candidate molecules. We have selected an unreported molecule and seven reported molecules and synthesized them. Photoluminescence spectrum measurements demonstrated that the DNMG can successfully design fluorescent molecules with 75% accuracy ( n = 6/8) and create an unreported molecule that emits fluorescence detectable by the naked eye.

Chiral 1,1’-binaphthyl-linked diporphyrin ‘tweezers’ (R)-1/(S)-1 and the corresponding zinc(II) complexes (R)-2/(S)-2 were prepared as chiral host molecules, and their utility for chiral analyses (especially enantiomeric excess (ee) determinations) were evaluated. Tris(1-n-dodecyl)porphyrins were used for the first time as the interacting units. Host capabilities of the diporphyrin tweezers were investigated by titrations with (R,R)- and (S,S)-cyclohexane-1,2-diamine (CHDA). The host molecules could be used as multichannel probes of ee by using UV-vis, circular dichroism (CD), fluorescence emission and 1H nuclear magnetic resonance (1H-NMR) methods. Chiral configurations could also be differentiated using CD or 1H-NMR spectroscopy. All three optical techniques give good resolution of ee with reasonable sensitivity considering the low concentrations used (ca. 10−6 mol·L−1). The ee determination of CHDA enantiomers using NMR spectroscopy is also possible because of the reasonably well separated resonances in the case of (R,R)- and (S,S)-CHDA. Non-metallated (R)-1/(S)-1 hosts could not be used to detect chiral information in a strongly acidic chiral guest. This work demonstrates the utility of 1,1’-binapthyl-linked chiral hosts for chiral analysis of ditopically interacting enantiomers.

A multichromophoric triad, ZnP–OxP–C60 containing porphyrin (ZnTPP hereafter ZnP), oxoporphyrinogen (OxP) and fullerene (C60) has been synthesized to probe the intramolecular dynamics of its electron and energy transfer in relation to the presence of the closely linked electron deficient OxP–C60 ‘special pair’, constructed as a mimic of the naturally occurring photosynthetic antenna-reaction center. The DFT optimized structure of the triad reveals the relative spatial remoteness of the ZnP entity with proximal OxP/C60 entities. Free-energetics of different energy and electron transfer events were estimated using spectral, computational and electrochemical studies, according to the Rehm–Weller approach. Femtosecond transient absorption spectral studies revealed energy transfer from 1ZnP* to OxP to yield ZnP–1OxP*–C60, and electron transfer to yield ZnP˙+–OxP–C60˙− and/or ZnP–OxP˙+–C60˙− charge seperated states. That is, the ZnP entity in the triad operates as both antenna and electron donor to generate relatively long-lived charge separated states thus mimicking the early photoevents of natural photosynthesis.

Materials chemists develop chemical compounds to meet often conflicting demands of industrial applications. This process may not be properly modeled by black-box optimization because the target property is not well defined in some cases. Herein, we propose a new algorithm for automated materials discovery called BoundLess Objective-free eXploration (BLOX) that uses a novel criterion based on kernel-based Stein discrepancy in the property space. Unlike other objective-free exploration methods, a boundary for the materials properties is not needed; hence, BLOX is suitable for open-ended scientific endeavors. We demonstrate the effectiveness of BLOX by finding light-absorbing molecules from a drug database. Our goal is to minimize the number of density functional theory calculations required to discover out-of-trend compounds in the intensity-wavelength property space. Using absorption spectroscopy, we experimentally verified that eight compounds identified as outstanding exhibit the expected optical properties. Our results show that BLOX is useful for chemical repurposing, and we expect this search method to have numerous applications in various scientific disciplines.

Singlet oxygen sensitization involving a class of hemiquinonoid-substituted resorcinarenes prepared from the corresponding 3,5-di-t-butyl-4-hydroxyphenyl-substituted resorcinarenes is reported. Based on variation in the molecular structures, quantum yields comparable with that of the well-known photosensitizing compound meso-tetraphenylporphyrin were obtained for the octabenzyloxy-substituted double hemiquinonoid resorcinarene reported herein. The following classes of compounds were studied: benzyloxy-substituted resorcinarenes, acetyloxy-substituted resorcinarenes and acetyloxy-substituted pyrogallarenes. Single crystal X-ray crystallographic analyses revealed structural variations in the compounds with conformation (i.e., rctt, rccc, rcct) having some influence on the identity of hemiquinonoid product available. Multiplicity of hemiquinonoid group affects singlet oxygen quantum yield with those doubly substituted being more active than those containing a single hemiquinone. Compounds reported here lacking hemiquinonoid groups are inactive as photosensitizers. The term ‘fuchsonarene’ (fuchson + arene of resorcinarene) is proposed for use to classify the compounds.

Herein, we report the face-selective chemical etching of fullerene crystals in solvent under ambient conditions of temperature and pressure. First, fullerene C60 nanorods (FNRs), fullerene C60 nanosheets (FNSs) and fullerene C70 cubes (FCs) were prepared using ultrasound assisted liquid–liquid interfacial precipitation (ULLIP). Chemical etching of these crystals was then performed using ethylene diamine (EDA), which results in selective etching at the ends of FNRs forming hollow-structured fullerene nanotubes. For two dimensional FNSs, etching occurs mostly at the upper and lower surfaces of the sheets with partial etching at the edges. For three dimensional FCs, etching occurs on all faces of the cubes leading to the formation of objects with a gyroid-like morphology. In addition to the excellent water dispersibility due to EDA functionalization, chemically etched fullerene nanostructures showed excellent vapor sensing performance selective for acid vapors (formic or acetic acids) over aromatic vapors (benzene or toluene). In contrast to the established yet costly lithography techniques used to make microstructures, this is a simple and scalable solution process, and it presents a low-cost strategy for which we have coined the term ‘beaker lithography’ for the construction of hollow fullerene nanostructures.

Meso-5,10,15,20-tetrakis-3,5-di-tert-butyl-4-oxocyclohexadienylideneporphyrinogen, OxP, is a versatile, highly colored chromophore derived from meso-5,10,15,20-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin. It exhibits a wide range of chromogenic responses to solvents (solvatochromism), anions and acidic media (halochromism) making it potentially useful as an analytical reagent. The chromogenic responses of OxP can be modulated by varying its chemical structure, and this is reviewed here based on the introduction of substituents at central nitrogen atoms or pyrrolic [Formula: see text]-positions. OxP and its N-alkylated derivates Bn2OxP and Bn4OxP have been used to estimate acidity in non-polar solvents. Bn2OxP can also be used to determine enantiomeric excesses of chiral substances. N-alkylation has also been used to introduce higher functional groups such as porphyrins to prepare self-assembling systems. [Formula: see text]-Substitution has been used to introduce selectivity of anion interactions including towards basic anions (fluoride, cyanide) and polyoxoanions (nitrate, perchlorate, etc.). These aspects make OxP a highly adaptable tetrapyrrole molecule for sensing and other applications.

Two octahalogenated nickel(II) hydroxyphenylporphyrins were synthesized and characterized as to their electrochemical and spectroscopic properties as well as their reactivity in neutral, acidic, and basic nonaqueous media. The newly synthesized complexes are represented as NiPorCl

Interactions of anionic guests with a tritopic peripherally functionalized conjugated calix[4]pyrrole host (1) prepared using a regioselective synthetic method is reported. The regioselectivity of synthesis relies on selective N-alkylation of the calix[4]pyrrole caused by peripheral substitution of one pyrrole group with subsequent N-alkylation at the opposing pyrrole group termed by us ‘knock-on’ regioselectivity. The resulting host molecule exhibits anion interactions with common chloride and nitrate anions enhanced by an order of magnitude over the parent conjugated calix[4]pyrrole. Combined analysis of 1H NMR and UV-vis spectroscopic titration data enabled an evaluation of binding strengths of anions with the host KA in a binding model where the salt dissociation process is also incorporated in the form of its dissociation constant Kd. Anions could be classified as two types based on their interactions with 1: Type A anions (chloride, nitrate, perchlorate, hydrogensulphate) associate as 1 : 1 complexes through hydrogen bonding while interactions involving Type B anions (acetate, fluoride, dihydrogenphosphate) are complicated by host deprotonation and/or countercation association. Hosts based on rim-functionalized calix[4]pyrroles such as 1 represent a promising new family of chromophores for estimation of biologically relevant anions or other species.

Correlations between molecular properties and structures, such as those between the absorption wavelength and conjugate length, are beneficial for designing materials and controlling their properties. However, determining the molecular structures that correlate with the target molecular properties (such as molecular fluorescence) is not an easy task. In this study, we have used a de novo molecule generator (DNMG) coupled with quantum-chemical computation (QC) to develop new fluorescent molecules, which are garnering significant attention in various disciplines. With massive parallel computation (1024 cores, 5 days), DNMG has produced 3,643 candidate molecules within the density functional theory (DFT; one of QC) framework. Among the generated molecules, we have selected an unreported molecule and synthesized it for photoluminescence spectrum measurement. Our experimental verification demonstrated that DNMG can successfully create a new molecule which emits fluorescence detectable by the naked eye, as predicted by the DFT.

Nitrogen and phosphorus-containing ions such as ammonium, nitrates and phosphates are anthropogenic pollutants while ammonium nitrate may be diverted for nefarious purposes in improvised explosive devices. Crown ether-oxoporphyrinogen conjugates (OxP-crowns) are used to selectively detect nitrates, especially their ion pairs with K+ and NH4 + , based on ion pair complexation of OxP-crowns under phase transfer conditions. The presence of phosphate and carbonate lead to deprotonation of OxP-crowns. OxP-1N18C6 is capable of extracting ion pairs with nitrate from aqueous phase leading to a selective chromogenic response. Deprotonation of the OxP moiety leads to [OxP- ]-1N18C6[K+ ] and is promoted by crown ether selective cation binding coupled with hydration of basic oxoanions, which are constrained to remain in the aqueous phase. This work illustrates the utility of molecular design to exploit partitioning and ion hydration effects establishing the selectivity of the chromogenic response.

A multichromophoric triad, ZnP-OxP-C60 containing porphyrin (ZnTPP hereafter ZnP), oxoporphyrinogen (OxP) and fullerene (C60) has been synthesized to probe the intramolecular dynamics of its electron and energy transfer in relation to the presence of the closely linked electron deficient OxP-C60 'special pair', constructed as a mimic of the naturally occurring photosynthetic antenna-reaction center. The DFT optimized structure of the triad reveals the relative spatial remoteness of the ZnP entity with proximal OxP/C60 entities. Free-energetics of different energy and electron transfer events were estimated using spectral, computational and electrochemical studies, according to the Rehm-Weller approach. Femtosecond transient absorption spectral studies revealed energy transfer from 1ZnP* to OxP to yield ZnP-1OxP*-C60, and electron transfer to yield ZnP˙+-OxP-C60˙- and/or ZnP-OxP˙+-C60˙- charge seperated states. That is, the ZnP entity in the triad operates as both antenna and electron donor to generate relatively long-lived charge separated states thus mimicking the early photoevents of natural photosynthesis.

A new class of bifunctional hydrogen-bond donor organocatalyst using oxoporphyrinogens with increased intramolecular hydrogen-bond donor distances is reported. Oxoporphyrinogens are highly non-planar rigid macrocycles containing a multiple hydrogen bond forming binding site. In this work we report the first example of non-planar OxPs as hydrogen-bond donor catalysts. The introduction of β-substituents is key to the catalytic activity and the catalysts are able to catalyze 1,4-conjugate additions and sulfa-Michael additions, as well as, Henry and aza-Henry reactions at low catalyst loadings (≤ 1 mol%) under mild conditions. Preliminary mechanistic studies have been carried out and a possible reaction mechanism has been proposed based on the bi-functional activation of both substrates through hydrogen-bonding interactions.

Four new 2-amino-5,7-dimethyl-1,8-naphthyridine derivatives (1–4) possessing urea, amide-imidazolium salt, amide-azide, or amide-triazole moieties were synthesized in good to excellent yields by derivatization of 2-amino-5,7-dimethyl-1,8-naphthyridine. We examined their anion recognition abilities towards different anions such as fluoride, chloride, bromide, iodide, nitrate, dihydrogen phosphate, cyanide, hexafluorophosphate, perchlorate, hydrogen sulphate and acetate by 1H NMR and UV-Vis spectroscopy. Among various 2-amino-5,7-dimethyl-1,8-naphthyridine derivatives, only 1a and 2 showed spectroscopic and colorimetric change when treated with fluoride ions among other anions. The F− ions first established a hydrogen-bonding interaction with 1a to give the most stable 1 : 1 complex and then, after addition of a second equivalent, the F− ions induced urea deprotonation due to the formation of HF2−. Moreover, 2 underwent deprotonation of amide –NH proton after the addition of 1 equiv. of fluoride ions. The action of the probes was thoroughly investigated by DFT calculations that also supported the H-bonding induced deprotonation sensing mechanism.

Copper(II) or Nickel(II) complexes of 5,10,15,20-tetrakis(3,4-dioxo-5-t-butylcyclohexa-1,5-dienyl)porphyrin (diOxPM, M = Ni, Cu) exhibited a hypsochromic shift in the B-band as compared to the respective 5,10,15,20-tetrakis(3,5-di-t-butyl-4′-hydroxyphenyl)porphyrin (H2-dtBTPP) and meso-tetrakis(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadienylidene)porphyrinogen (OxP). Thorough investigation of the electrochemical properties of diOxPM (M = Ni, Cu), OxP and H2-dtBTPP lead us to the important observation that the first reduction of diOxPM (M = Ni and Cu) is very much anodically shifted (ΔEredn = 1.1 V) as compared to that of M-dtBTPP (M = Cu or Ni) due to the presence of the strongly electron withdrawing cyclohexadienyl groups. These electron-deficient meso-tetrakis(3,4-benzoquinone)-substituted Ni(II) and Cu(II) porphyrins exhibited very high binding constants (1.5 × 109–2.5 × 107 M−2) with F− and CN− and can be used to distinguish them from other anions by UV-Vis spectrophotometry. Solvatochromism was combined with anion binding in an attempt to provide the axial ligation mechanism of CN− and F− ions. These highly electron deficient porphyrins act as F− and CN− chemosensors in nonaqueous media. However, these porphyrins detect only CN− ions in an aqueous medium but remain insensitive towards F− ions due to high solvation of F− ions in water.

Background and aims A sizable body of research has elucidated the significant role of psychological reactions to trauma on pain coping and outcomes. In order to best inform intervention development and clinical care for patients with both trauma and pain at the tertiary care level, greater clarity is needed regarding the magnitude of these effects and the specific pathways through which they may or may not function at the time of first presentation to such a treatment setting. To achieve this, the current study examined the cross-sectional relationships between traumatic etiology of pain, psychological distress (anger, depressive symptoms, and PTSD symptoms), and pain outcomes (pain catastrophizing, physical function, disability status). Methods Using a structural path modeling approach, analyses were conducted using a large sample of individuals with chronic pain (n = 637) seeking new medical evaluation at a tertiary pain management center, using the Collaborative Health Outcomes Information Registry (CHOIR). We hypothesized that the relationships between traumatic etiology of pain and poorer pain outcomes would be mediated by higher levels of psychological distress. Results Our analyses revealed modest relationships between self-reported traumatic etiology of pain and pain catastrophizing, physical function, and disability status. In comparison, there were stronger relationships between indices of psychological distress and pain catastrophizing, but a weaker pattern of associations between psychological distress and physical function and disability measures. Conclusions To the relatively small extent that self-reported traumatic etiology of pain correlates with pain-related outcomes, these relationships appear to be due primarily to the presence of psychiatric symptoms and manifest most notably in the context of psychological responses to pain (i.e. catastrophizing about pain). Implications Findings from this study highlight the need for early intervention for patients with traumatic onset of pain and for clinicians at tertiary pain centers to include more detailed assessments of psychological distress and trauma as a component of comprehensive chronic pain treatment.

A new class of bifunctional hydrogen-bond donor organocatalyst using oxoporphyrinogens with increased intramolecular hydrogen-bond donor distances is reported. Oxoporphyrinogens are highly non-planar rigid macrocycles containing a multiple hydrogen bond forming binding site. In this work we report the first example of non-planar OxPs as hydrogen-bond donor catalysts. The introduction of β-substituents is key to the catalytic activity and the catalysts are able to catalyze 1,4-conjugate additions and sulfa-Michael additions, as well as, Henry and aza-Henry reactions at low catalyst loadings (≤ 1 mol%) under mild conditions. Preliminary mechanistic studies have been carried out and a possible reaction mechanism has been proposed based on the bi-functional activation of both substrates through hydrogen-bonding interactions.

A new class of bifunctional hydrogen-bond donor organocatalyst using oxoporphyrinogens with increased intramolecular hydrogen-bond donor distances is reported. Oxoporphyrinogens are highly non-planar rigid macrocycles containing a multiple hydrogen bond forming binding site. In this work we report the first example of non-planar OxPs as hydrogen-bond donor catalysts. The introduction of β-substituents is key to the catalytic activity and the catalysts are able to catalyze 1,4-conjugate additions and sulfa-Michael additions, as well as, Henry and aza-Henry reactions at low catalyst loadings (≤ 1 mol%) under mild conditions. Preliminary mechanistic studies have been carried out and a possible reaction mechanism has been proposed based on the bi-functional activation of both substrates through hydrogen-bonding interactions.

Simple oxoporphyrinogen (OxP) derivatives are excellent colorimetric sensors for a variety of analytes including anions, acidity and enantiomeric excess. More recently, this family of compounds has grown to include rim-functionalized compounds, which also exhibit colorimetric properties. In this work, we have prepared differently rim-functionalized OxPs and we will present their properties with respect to sensing, including selective anion binding, ion pair sensing and coupled sensing of other important polluting species. The sensing properties of OxPs rely on intermolecular hydrogen bonding interactions which, in turn, imply their possible applications in organocatalysis. These properties will be described with an emphasis on the identity of macrocyclic substituents, and how catalytic activity of the OxP macrocycles is established. Structural aspects of OxPs influencing their sensing and organocatalytic activities will be discussed.

Singlet oxygen (1O2) is an excited state of the dioxygen molecule with higher reactivity compared to the ground electronic state. Therefore, singlet oxygen is an important species used for oxidation of organic compounds, degradation of environmental pollutants, inactivation of bacteria or treatment of tumours. Metal-organic frameworks (MOFs) are suitable as carriers of 1O2 photosensitizers because of the permeability of their porous structure to gas molecules and effective prevention of aggregation of the photosensitizer chromophores. Moreover, the character of MOFs enables easy preparation of multifunctional materials combining 1O2 generation with other properties. In this review we summarize recent advances in the development of MOFs for 1O2 generation. We focus on the three main fields of application of these materials: oxidation of organic compounds, degradation of pollutants and photodynamic therapy. Each of these fields has its own specific requirements, which is reflected in the design of appropriate materials.

A new series of aryloxyporphyrins bearing benzyl and naphthyl substituents viz., ZnTBPP (1), ZnTNPP (2) and ZnONPP (3) has been synthesized and characterized by UV-vis, fluorescence and 1H NMR spectroscopic techniques and mass spectrometry. 1–3 have been utilized as donors to interact with fullerene (C[Formula: see text] acceptor to form 1:1 complex in toluene at 298 K. The subsequent investigation into quenching measurements with concomitant increase in fullerene concentration revealed effective quenching constants. The calculated association constants were in the order of 103 M[Formula: see text]. However, ZnTNPP (2) exhibited higher binding constant as compared to other analogs due to effective [Formula: see text]–[Formula: see text] interactions. ZnONPP (3) exhibited 3.4 times lower association constant than ZnTNPP (2) due to steric hindrance offered by meso-(3,5-dinapthyloxyphenyl) groups. The geometric and electronic structure of Zn(II) porphyrin-fullerene dyad was probed by DFT calculations which suggested the possibility of charge transfer from meso-aryloxyporphyrin core to fullerene C[Formula: see text].

Simple oxoporphyrinogen (OxP) derivatives are excellent colorimetric sensors for a variety of analytes including anions, acidity and enantiomeric excess. More recently, this family of compounds has grown to include rim-functionalized compounds, which also exhibit colorimetric properties. In this work, we have prepared differently rim-functionalized OxPs and we will present their properties with respect to sensing, including selective anion binding, ion pair sensing and coupled sensing of other important polluting species. The sensing properties of OxPs rely on intermolecular hydrogen bonding interactions which, in turn, imply their possible applications in organocatalysis. These properties will be described with an emphasis on the identity of macrocyclic substituents, and how catalytic activity of the OxP macrocycles is established. Structural aspects of OxPs influencing their sensing and organocatalytic activities will be discussed.

We utilized the potential applications of 1,8-naphthyridine-based sensors for the detection of various nitroaromatics such as picric acid (PA), 3-nitrophenol (NP), 2,4-dinitrotoluene (DNT), 1,3-dinitrobenzene (DNB), 4-nitrotoluene (NT), nitrobenzene (NB) and nitromethane (NM). Among the various nitroaromatic analogues, nap-OH (1) and nap-Cl (2) sense picric acid (PA) much more efficiently and with very low detection limits (1.12 and 0.96 ppm, respectively), owing to favourable electron and/or energy transfer mechanisms along with potential electrostatic interactions. Interestingly, both sensors 1 and 2 detect PA in aqueous media (H2O/CH3OH, 8 : 2) with the same quenching efficiency as in neat CH3OH, resulting in cheap, sensitive and environmentally friendly detection methodology. Therefore, use of these molecules for picric acid detection in aqueous and methanolic solutions, having low detection limits along with exceptional quenching constants (kSV) meets the present need. In addition, sensors 1 and 2 exhibit instant visualization of trace amounts of PA in both the solid-state and when using test strips.

Dicyanovinyl appended β-pyrrole substituted porphyrins have been synthesized and utilized as chemodosimeters for ratiometric and colorimetric sensing of cyanide ions. In addition to meso-tetraphenylporphyrin (TPP) based system, we have designed and synthesized octaphenylporphyrin (OPP) based moderately nonplanar systems. These systems also depicted effective π-conjugation between the pyrrole ring and its olefinic substituent which is reflected in the UV-vis absorption spectra as the red-shifting of both Soret and Q-bands and possibly the splitting of the absorption Soret band. This article describes the single crystal X-ray structure, electronic spectral and electrochemical redox properties of these porphyrin chemodosimeters. The stable anionic-porphyrin species formed after addition of CN− ions has a blue shifted unperturbed absorption spectrum due to the disruption of electronic resonance and charge-transfer interactions between the β-dicyanovinyl acceptor and porphyrin core. The probes exhibited excellent selectivity towards CN− over other anions such as F−, Cl−, Br−, NO3−, H2PO4−, AcO−, I−, HSO4−, ClO4− and PF6−. The action of the chemodosimeters were investigated by 1H-NMR titrations, ESI-mass spectrometry, electrochemical studies and DFT calculations which supported the formation of cyanide addition adduct (porphyrin–CN)−. These chemodosimeters depicted lowest detection limit (LOD) of 0.023–0.082 ppm, which is very much lower than the permissible limit (0.2 ppm) and other porphyrinoids reported till date. These porphyrins are also able to detect cyanide ions in (9:1, v/v) CH3CN:H2O mixture with low detection limits thereby providing practical applicability of these chemodosimeters.

Two new receptors viz. 2-bromoacetamido-5,7-dimethyl-1,8-naphthyridine (1a) and 2-chloroacetamido-5,7-dimethyl-1,8-naphthyridine (1b) containing 1,8-naphthyridine as fluorophore unit have been designed and synthesised. These receptors exhibited very high selectivity for F− ions among the various anions tested such as H2PO4−, OAc−, Cl−, Br−, I−, HSO4−, PF6−, ClO4−, BF4− and NO3− owing to anion-induced deprotonation of the amide NH by F− ions. Among the various cations tested (Na+, Ag+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+ and Mn3+), 1a exhibited selective detection of Hg2+ ions by binding with N1 and N8 atoms of the naphthyridine moiety. Receptor 1a has been explored as a dual-ion detector for F− and Hg2+ ions in two contrasting modes (fluorescence ‘turn-on’ and ‘turn-off’) which is supported by spectroscopic and lifetime measurements. 1a exhibited lower detection limits for F− (0.4 ppm) and Hg2+ (2.4 ppm) ions. These receptors were recovered from anionic species of 1a formed after addition of F− ions by treating with protic solvents such as CH3OH. The mode of binding was also confirmed by spectroscopic and DFT studies. The chemical inputs of F− and Hg2+ ions generate an output which satisfies the condition of two-input INHIBIT logic operators.

The synthesis of three new classes of mixed β-pyrrole substituted tetraphenylporphyrins, MTPP(R), MTPP(Br)2(R) (where R = -CH[double bond, length as m-dash]C(CN)2, -CH[double bond, length as m-dash]C(CN)(COOC2H5), -CH[double bond, length as m-dash](CN)(COOH) and M = 2H, Ni(ii), Cu(ii)) and MTPP(NO2)(Ph-p-R')2 (R' = -CHO and -CH[double bond, length as m-dash]C(CN)2 and M = 2H, Ni(ii), Cu(ii)) have been reported. The crystal structures of CuTPP(Br)2-ECA (7a), NiTPP(NO2)(Ph-p-CHO)2 (9) and NiTPP(NO2)(Ph-p-CH[double bond, length as m-dash](CN)2)2 (10) are highly nonplanar among β-trisubstituted porphyrins reported to date as evidenced from the mean displacement of β-pyrrole carbon (ΔCβ) in the range ±(0.39-0.674) A. The olefin mediated ethyl cyanoacetate is in plane with the porphyrin core in CuTPP(Br)2-ECA (the dihedral angle relative to the pyrrole NC4-mean plane is 39.81°) while dicyanovinyl stays aside for NiTPP(NO2)(Ph-p-CH[double bond, length as m-dash](CN)2)2 (dihedral angles relative to the pyrrole NC4-mean plane are 75.03° and 67.47°). NiTPP-MN (2), NiTPP-ECA (3), NiTPP(Br)2-MN (6) and NiTPP(Br)2-ECA (7) act as chemodosimeters for toxic CN- ions whereas NiTPP-CAA (4) and NiTPP(Br)2-CAA (8) act as chemosensors to detect toxic ions such as CN-, F- and OAc- depending on the acceptor strength and an obstacle in the conjugation pathway. The dicyanovinyl group in the phenyl olefinic-mediated porphyrin NiTPP(NO2)(Ph-p-CH[double bond, length as m-dash](CN)2)2 (10) also acts as chemodosimeter for CN- ions but no vivid changes are observed via different spectroscopic methods.

Two highly non-planar octahalogenated nickel(II) porphyrins were characterized for the first time as to their electrochemical and spectroscopic properties as well as their chemical reactivity in nonaqueous media. The complexes have the structures shown in Chart 1. Chart 1. Structures of investigated porphyrins. The UV-vis spectra of NiPorCl8 and NiPorBr8 vary with solvent and degree of axial coordination and are substantially different than spectra of the unhalogenated NiPor parent porphyrin. The NiPorBr8 and NiPorCl8 spectra are stable with time and interpreted in terms of four or six-coordinated derivatives in 14 different nonaqueous solvents but this is not the case for NiPorCl8 in DMF or DMSO where a transient 6-coordinate solvated complex is initially formed upon dissolving the compound followed by formation of a porphodimethene in solution. The combination of eight β-halogens and four meso-t-butyl-hydroxyphenyl groups on the NiPorX8 complexes exerts a powerful influence on the electrochemistry which is characterized by up to five redox reactions, the first 2 or 3 of which are irreversible at room temperature and assigned as involving the easily reducible meso-hydroxyphenyl groups followed by reduction of the π-conjugated system at more negative potentials. A rapid homogeneous chemical reaction occurs after the first electron transfer giving as the final product a nickel(II) porphodimethane at the electrode surface. This was confirmed by comparisons between redox potentials and UV-visible spectra of the in situ generated electroreduction products with that of chemically synthesized porphodimethenes formed in a reaction between NiPorCl8 and the added anions F-, CN-, OAc- or H2PO4 -.

β-Functionalization of meso-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin with electron acceptors such as formyl and dicyanovinyl has been reported for the first time. 2-Formyl-5,10,15,20-tetrakis(3',5'-di-tert-butyl-4'-hydroxyphenyl)porphyrinatocopper(ii) (Cu-TDtBHPP-CHO) crystallizes in the triclinic space group P1[combining macron], [a = 10.8479(4) A, b = 14.6207(5) A, c = 15.9745(5) A, V = 2198.97(13) A3] and exhibits an almost planar structure and a square planar geometry. β-Formyl/dicyanovinyl substituted porphyrins such as Cu-TDtBHPP-CHO, Ni-TDtBHPP-CHO, Cu-TDtBHPP-MN (1), Ni-TDtBHPP-MN (2) and H2-TDtBHPP-MN (3) exhibited red-shifted optical absorption features (Δλmax = 13-40 nm) in CH2Cl2 compared to the corresponding MTPPs. β-Dicyanovinyl substituted porphyrins were developed as a quantitatively operating 'lab-on-a-molecule' for the visual detection of F- and CN- ions. Having a CN- ion responsive dicyanovinyl moiety and a F- ion responsive redox-active 3,5-di-tert-butyl-4-hydroxyphenyl groups, they detect F- and CN- ions simultaneously by switching unique structural changes between porphyrin, porphodimethene and porphyrinogen along with distinct colour changes which were monitored by UV-Vis-NIR, fluorescence and NMR spectroscopic techniques.