Mild selective photochemical oxidation of an organic sulfide using OxP-polyimide porous polymers as singlet oxygen generators.

A series of porous organic polymers based on a singlet oxygen generating oxoporphyinogen ('OxP') has been successfully prepared from a pseudotetrahedral OxP-tetraamine precursor (OxP(4-NH2Bn)4) by its reaction with tetracarboxylic acid dianhydrides under suitable conditions. Of the compounds studied, those containing naphthalene (OxP-N) and perylene (OxP-P) spacers, respectively, have large surface areas (~530 m2 g-1). On the other hand, the derivative with a simple benzene spacer (OxP-B) exhibits the best 1O2 generating capability. Although the starting OxP-tetraamine precursor is a poor 1O2 generator, its incorporation into OxP POPs leads to a significant enhancement of 1O2 productivity, which is largely due to the transformation of NH2 groups to electron-withdrawing diimides. Overall 1O2 production efficacy of OxP-POPs under irradiation by visible light is significantly improved over the common reference material PCN-222. All the materials OxP-B, OxP-N and OxP-P promote oxidation of thioanisole involving conversion of ambient triplet state oxygen to singlet oxygen under visible light irradiation and its reaction with the sulfide. Although the reaction rate of the oxidation promoted by OxP POPs is generally lower than for conventional materials (such as PCN-222) or previously studied OxP derivatives, undesired overoxidation of the substrate to methyl phenyl sulfone is suppressed. For organic sulfides, selectivity of oxidation is especially important for detoxification of mustard gas (bis(2-chloroethyl)sulfide) or similarly toxic compounds since controlled oxidation leads to the low toxicity bis(2-chloroethyl)sulfoxide while overoxidation leads to intoxification (since bis(2-chloroethyl)sulfone presents greater toxicity to humans than the sulfide substrate). Therefore, OxP POPs capable of promoting selective oxidation of sulfides to sulfoxides have excellent potential to be used as mild and selective detoxification agents.

Oxoporphyrinogen (OxP) is a unique chromophore compound in that it is intrinsically de-aggregated allowing large quantum yields of singlet oxygen generation. Due to its structure, OxP is also an ideal building block for porous systems. In this work, we describe the first incorporation of OxP in highly stable microporous polymers strongly enhanced singlet oxygen generation for selective oxidation of organic sulfides to sulfoxides (as a model reaction) under heterogeneous conditions. The novelty of this work lies in the high stability and easy recovery of the materials, the synergetic enhancement of singlet oxygen generation in the polymers over the starting OxP, and the excellent selectivity for the oxidation reaction.

Tools to enable the study and translation of supramolecular amphiphiles.

This tutorial review focuses on providing a summary of the key techniques used for the characterisation of supramolecular amphiphiles and their self-assembled aggregates; from the understanding of low-level molecular interactions, to materials analysis, use of data to support computer-aided molecular design and finally, the translation of this class of compounds for real world application, specifically within the clinical setting. We highlight the common methodologies used for the study of traditional amphiphiles and build to provide specific examples that enable the study of specialist supramolecular systems. This includes the use of nuclear magnetic resonance spectroscopy, mass spectrometry, X-ray scattering techniques (small- and wide-angle X-ray scattering and single crystal X-ray diffraction), critical aggregation (or micelle) concentration determination methodologies, machine learning, and various microscopy techniques. Furthermore, this review provides guidance for working with supramolecular amphiphiles in in vitro and in vivo settings, as well as the use of accessible software programs, to facilitate screening and selection of druggable molecules. Each section provides: a methodology overview - information that may be derived from the use of the methodology described; a case study - examples for the application of these methodologies; and a summary section - providing methodology specific benefits, limitations and future applications.

Selective Detection of Toxic C1 Chemicals Using a Hydroxylamine-Based Chemiresistive Sensor Array.

Formaldehyde (FA) is a deleterious C1 pollutant commonly found in the interiors of modern buildings. C1 chemicals are generally more toxic than the corresponding C2 chemicals, but the selective discrimination of C1 and C2 chemicals using simple sensory systems is usually challenging. Here, we report the selective detection of FA vapor using a chemiresistive sensor array composed of modified hydroxylamine salts (MHAs, ArCH2ONH2·HCl) and single-walled carbon nanotubes (SWCNT). By screening 32 types of MHAs, we have identified an ideal sensor array that exhibits a characteristic response pattern for FA. Thus, trace FA (0.02-0.05 ppm in air) can be clearly discriminated from the corresponding C2 chemical, acetaldehyde (AA). This system has been extended to discriminate methanol (C1) from ethanol (C2) in combination with the catalytic conversion of these alcohols to their corresponding aldehydes. Our system offers portable and reliable chemical sensors that discriminate the subtle differences between C1 and C2 chemicals, enabling advanced environmental monitoring and healthcare applications.

De novo creation of a naked eye-detectable fluorescent molecule based on quantum chemical computation and machine learning.

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.

Anion-enhanced excited state charge separation in a spiro-locked N-heterocycle-fused push-pull zinc porphyrin.

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.

Pushing property limits in materials discovery via boundless objective-free exploration.

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.

Selective Phase Transfer Reagents (OxP-crowns) for Chromogenic Detection of Nitrates Especially Ammonium Nitrate.

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.

Electron and energy transfer in a porphyrin-oxoporphyrinogen-fullerene triad, ZnP-OxP-C60.

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.

Supramolecular ultrafast energy and electron transfer in a directly linked BODIPY-oxoporphyrinogen dyad upon fluoride ion binding.

A directly linked BODIPY-oxoporphyrinogen dyad has been newly synthesized and occurrence of sequential photoinduced energy and electron transfer upon fluoride anion binding to oxoporphyrinogen has been demonstrated by spectral, electrochemical and femtosecond transient absorption studies.

Self-reported traumatic etiology of pain and psychological function in tertiary care pain clinic patients: a collaborative health outcomes information registry (CHOIR) study.

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.

Nanomolecular singlet oxygen photosensitizers based on hemiquinonoid-resorcinarenes, the fuchsonarenes.

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.

Synthesis, Electrochemistry, and Reversible Interconversion among Perhalogenated Hydroxyphenyl Ni(II) Porphyrins, Porphodimethenes, and Porpho-5,15-bis-paraquinone Methide.

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 NiPorCl8 and NiPorBr8, where Por is the dianion of meso-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin. The UV-vis spectra of NiPorCl8 and NiPorBr8 vary with the solvent and degree of axial coordination but are almost identical to each other in a given solvent. These spectra are also substantially different from that of the unhalogenated NiPor parent porphyrin (which resembles nickel tetraphenylporphyrin, NiTPP), and they also differ from the spectra of ß-octahalogenated NiTPPCl8 and NiTPPBr8 under the same solution conditions. The NiPorX8 spectra are stable with time and interpreted in terms of 4- or 6-coordinate derivatives in 13 different nonaqueous solvents. This is not the case, however, in DMF or DMSO, where a transient six-coordinate complex is initially formed upon dissolving the NiPorCl8, followed by the formation of an air-oxidized porphodimethene-like product called porpho-5,15-bis-paraquinone methide, with the time of this chemical transformation depending upon the concentration of the porphyrin in solution. The initial species formed from NiPorCl8 and NiPorBr8 after the first one-electron addition in CH2Cl2 is stable for short times at -60 °C, but this is not the case at room temperature, where a rapid homogeneous chemical reaction occurs. Four additional redox reactions are also observed in CH2Cl2, and the UV-visible spectra of several in-situ-generated electroreduction products are compared with that of chemically synthesized porphodimethenes formed in neutral, acidic, and basic solutions of CH2Cl2 containing acid in the form of TFA or base in the form of TBA+X, where X = OAc-, CN-, and OH-. Finally, a reversible electrochemically driven conversion between the Ni(II) hydroxyphenylporphyrin and a reduced porphodimethene or oxidized porphyrin-like product, porpho-5,15-bis-paraquinone methide, is described.

Knock-on synthesis of tritopic calix[4]pyrrole host for enhanced anion interactions.

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.

ß-Dicyanovinyl substituted porphyrinogen: synthesis, a reversible sensor for picric acid among explosives and a unique sensor for cyanide and fluoride ions by switching between various porphyrinoid states.

ß-Dicyanovinyl substituted porphyrinogen (OxP-MN) was synthesized and utilized as a novel multifunctional sensor for the detection of biologically and environmentally important analytes. OxP-MN (1) acts as a selective and reversible probe for rapid colorimetric detection of picric acid (PA) among other nitroaromatics by switching between two porphyrinoid states. This system displayed a higher ß2 value of 1.7 × 108 M-2 and was able to detect PA down to 1.12 ppm (4.99 µM). ß-Dicyanovinyl substituted porphyrinogen (OxP-MN) reported here contains a porphyrinogen anion binding site and a dicyanovinyl group as a cyanide-dependent reactive subunit. OxP-MN displayed the first evidence that a ß-electron acceptor through a vinyl linker in the case of porphyrinogen results in only an abated shift in the spectrum in contrast to its porphyrin analogues. Porphyrinogen OxP-MN (1) can be switched between a number of porphyrinoid states such as metalloporphodimethene, metalloporphyrin, porphyrinogen, etc. by using CN-, F- and other basic anions. In addition, OxP-MN unveils the unique property of detecting toxic cyanide ions and fluoride ions when "hidden" within a mixture of other anions. Also, OxP-MN behaves as a dual sensor for picric acid and basic anions such as F-, CN-, OAc-, and H2PO4-via the indicator displacement assay under the unrestricted queue.

An insight into the communication between ß-olefin/phenyl olefin-mediated acceptors and porphyrin π-system: a way to establish porphyrin based chemodosimeters and chemosensors.

The synthesis of three new classes of mixed ß-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 ß-trisubstituted porphyrins reported to date as evidenced from the mean displacement of ß-pyrrole carbon (ΔCß) in the range ±(0.39-0.674) Å. 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.

Switching between porphyrin, porphodimethene and porphyrinogen using cyanide and fluoride ions mimicking volatile molecular memory and the 'NOR' logic gate.

ß-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) Å, b = 14.6207(5) Å, c = 15.9745(5) Å, V = 2198.97(13) Å3] and exhibits an almost planar structure and a square planar geometry. ß-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. ß-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.