Ultra-sensitive gas phase detection of 2,4,6-trinitrotoluene by non-covalently functionalized graphene field effect transistors.

The high energy density (4.2 MJ kg-1) and low vapour pressure (7.2 × 10-9 atm) of chemical explosives such as TNT (2,4,6-trinitrotoluene) pose a grave security risk demanding immediate attention. Detection of such hazardous and highly challenging chemicals demands specific, ultra-sensitive and rapid detection platforms that can concomitantly transduce the signal as an electrical readout. Although chemo-sensitive strategies have been investigated, the majority of them are restricted to detecting TNT from solutions and are therefore not implementable in real-time, on-field situations. Addressing this demand, we report an ultra-sensitive (parts-per-billion) and rapid (∼40 s) detection platform for TNT based on non-covalently functionalized graphene field effect transistors (GFETs). This multi-parametric GFET detector exhibits a reliable and specific modulation in its Dirac point upon exposure to TNT in the vapour phase. The chemical specificity provided by 5-(4-hydroxyphenyl)-10,15,20-tri(p-tolyl) zinc porphyrin (ZnTTPOH) is synergistically combined with the high surface sensitivity of graphene through a non-covalent functionalization approach to realise p-doped GFETs (Zn-GFETs). Such a FET platform exhibits extremely sensitive shifts in Dirac point (ΔDP) that correlate with the number of nitro groups present in the analyte. Analytes with mono-, di-, and tri-nitro substituted aromatic molecules exhibit distinctly different ΔDP, leading to unprecedented specificity towards TNT. Additionally, the Dirac point of Zn-GFETs is invariant for common and potential interferons such as acetone and 2-propanol (perfume emulsifiers) thereby validating their practical applicability. Furthermore, the ΔDP is also manifested as changes in the contact potential of GFETs, indicating that sub-monolayer coverage of ZnTTPOH is sufficient to modulate the transfer characteristics of GFETs over an area 1000 times larger than the dopant dimensions. Specifically, ZnTTPOH-functionalized GFETs exhibit p-doped behaviour with positive ΔDP with respect to pristine GFETs. Such p-doped Zn-GFETs undergo selective charge-transfer mediated interactions with TNT resulting in enhanced electron withdrawal from Zn-GFETs. Thus the ΔDP shifts to a higher positive gate voltage leading to the dichotomous combination of the highest signal generation (1.2 × 1012 V mol-1) with ppb level molecular sensitivity. Significantly, the signal generated due to TNT is 105 times higher in magnitude compared to other potential interferons. The signal reliability is established in cross-sensitivity measurements carried out with a TNT-mDNB (1 : 10 molar ratio) mixture pointing to high specificity for immediate applications under atmospherically relevant conditions pertaining to homeland security and global safety.

Construction of Novel Cyclic Tetrads by Axial Coordination of Thiaporphyrins to Tin(IV) Porphyrin.

We report the formation of new cyclic porphyrin tetrads 1 and 2, which were obtained from the reaction between dihydroxytin(IV) porphyrin and cis-dihydroxy-21-thiaporphyrin/21,23-dithiaporphyrin. The unique oxophilicity of tin(IV) porphyrin was the driving force for the formation of these tetrads. Moreover, these novel tetrads represent the first examples of cyclic porphyrins containing tin(IV) that are constructed exclusively on the basis of the "Sn-O" interaction without any other complementary, noncompetitive mode of interactions. The molecular structures of the cyclic tetrads have been investigated by matrix-assisted laser desorption ionization time-of-flight mass spectrometry, NMR spectroscopy, quantum-mechanical calculations, and, in one case, single-crystal X-ray crystallography. The X-ray structure revealed that the two cis-dihydroxy-N2S2 porphyrins were coordinated at the axial positions of two tin(IV) porphyrins, leading to the symmetric cyclic tetrad structure. The optical properties of tetrads were studied, and these compounds were stable under redox conditions. Preliminary photophysical studies carried out on the tetrads indicated efficient energy transfer from tin(IV) porphyrin to the thiaporphyrin unit, which highlights their potential applications in energy and electron transfer in the future.

A Stable Seven-Membered Heterocycle, Containing B, C, N, O, and P Atoms, inside a Smaragdyrin Macrocycle.

Unprecedented examples of smaragdyrin macrocycles containing seven membered heterocyclic rings were synthesized under simple reaction conditions in high yields. The heterocycle formed inside smaragdyrin macrocycle is rare example of heterocycle containing five different atoms, such as B, C, N, O, and P atoms. The mixed B(III) and P(V) complexes of smaragdyrin macrocycles showed new structural, spectral, and electrochemical properties.

Stereochemical modulation of emission behaviour in E/Z isomers of diphenyldipyrroethene from aggregation induced emission to crystallization induced emission.

Herein, we report the synthesis, separation and characterisation of the E- and Z-isomers of dipyrrolyldiphenylethene to study their emission behaviour in the aggregation state and solid state. The E-isomer showed pronounced aggregation induced emission (AIE) whereas the Z-isomer showed crystallization induced emission (CIE). The present study explains that the emission behaviour (AIE/CIE) is dependent on the inter/intra molecular interactions between the molecules. The study also confirms that restriction of intramolecular rotation (RIR) is the main cause of AIE/CIE in olefinic luminogens Tetraphenylethylene (TPE) type systems rather than E/Z isomerisation.

An efficient learning based approach for automatic record deduplication with benchmark datasets.

With technological innovations, enterprises in the real world are managing every iota of data as it can be mined to derive business intelligence (BI). However, when data comes from multiple sources, it may result in duplicate records. As data is given paramount importance, it is also significant to eliminate duplicate entities towards data integration, performance and resource optimization. To realize reliable systems for record deduplication, late, deep learning could offer exciting provisions with a learning-based approach. Deep ER is one of the deep learning-based methods used recently for dealing with the elimination of duplicates in structured data. Using it as a reference model, in this paper, we propose a framework known as Enhanced Deep Learning-based Record Deduplication (EDL-RD) for improving performance further. Towards this end, we exploited a variant of Long Short Term Memory (LSTM) along with various attribute compositions, similarity metrics, and numerical and null value resolution. We proposed an algorithm known as Efficient Learning based Record Deduplication (ELbRD). The algorithm extends the reference model with the aforementioned enhancements. An empirical study has revealed that the proposed framework with extensions outperforms existing methods.

Smaragdyrins: emeralds of expanded porphyrin family.

Porphyrins are tetrapyrrolic 18 π electron conjugated macrocycles with wide applications that range from materials to medicine. Expanded porphyrins, synthetic analogues of porphyrins that contain more than 18 π electrons in the conjugated pathway, have an increased number of pyrroles or other heterocyles or multiple meso-carbon bridges. The expanded porphyrins have attracted tremendous attention because of unique features such as anion binding or transport that are not present in porphyrins. Expanded porphyrins exhibit wide applications that include their use in the coordination of large metal ions, as contrasting agents in magnetic resonance imaging (MRI), as sensitizers for photodynamic therapy (PDT) and as materials for nonlinear optical (NLO) studies. Pentaphyrin 1, sapphyrin 2, and smaragdyrin 3 are expanded porphyrins that include five pyrroles or heterocyclic rings. They differ from each other in the number of bridging carbons and direct bonds that connect the five heterocyclic rings. Sapphyrins were the first stable expanded porphyrins reported in the literature and remain one of the most extensively studied macrocycles. The strategies used to synthesize sapphyrins are well established, and these macrocycles are versatile anion binding agents. They possess rich porphyrin-like coordination chemistry and have been used in diverse applications. This Account reviews developments in smaragdyrin chemistry. Although smaragdyrins were discovered at the same time as sapphyrins, the chemistry of smaragdyrins remained underdeveloped because of synthetic difficulties and their comparative instability. Earlier efforts resulted in the isolation of stable ß-substituted smaragdyrins and meso-aryl isosmaragdyrins. Recently, researchers have synthesized stable meso-aryl smaragdyrins by [3 + 2] oxidative coupling reactions. These results have stimulated renewed research interest in the exploration of these compounds for anion and cation binding, energy transfer, fluorescent sensors, and their NLO properties. Recently reported results on smaragdyrin macrocycles have set the stage for further synthetic studies to produce stable meso-aryl smaragdyrins with different inner cores to study their properties and potential for various applications.

Synthesis of BF2 complexes of prodigiosin type oligopyrroles.

We developed a simple, facile route for the synthesis of BF(2) complexes of prodigiosin type oligopyrroles and their cholesterol conjugates. This route gives an access to synthesize any desired meso-aryl-substituted 3-pyrrolyl BODIPYs which were not easily accessible earlier.

Hexa boron-dipyrromethene cyclotriphosphazenes: synthesis, crystal structure, and photophysical properties.

We have synthesized four examples of a cyclotriphosphazene ring appended with six boron-dipyrromethene dyes N(3)P(3)(BODIPY)(6) by adopting two different methods. In method I, 1 equiv of N(3)P(3)Cl(6) was treated with 6 equiv of meso-(o- or m- or p-hydroxyphenyl)boron-dipyrromethene in tetrahydrofuran (THF) in the presence of cesium carbonate. This afforded N(3)P(3)(BODIPY)(6) in yields ranging from 80 to 90%. In method II, we first prepared hexakis(p-formylphenoxy)cyclotriphosphazene N(3)P(3)(CHO)(6) by treating 1 equiv of N(3)P(3)Cl(6) with 6 equiv of 4-hydroxybenzaldehyde in the presence of cesium carbonate in THF. In the second step, N(3)P(3)(CHO)(6) was condensed with excess of pyrrole in the presence of catalytic amount of trifluoroacetic acid (TFA) in CH(2)Cl(2) at room temperature and afforded hexakis(p-phenoxy dipyrromethane)cyclotriphosphazene. In the last step, the hexakis(p-phenoxy dipyrromethane)cyclotriphosphazene was first oxidized with 6 equiv of DDQ in CH(2)Cl(2) at room temperature for 1 h followed by neutralization with triethylamine and further reaction with excess BF(3)·Et(2)O afforded the target N(3)P(3)(BODIPY)(6) in 16% yield. The route II was used only for the synthesis of one target compound whereas the route I was used for the synthesis of all four target compounds. The four compounds were characterized by mass, NMR, absorption, electrochemical, and fluorescence techniques. The crystal structure solved for one of the compounds revealed that the P(3)N(3) ring is slightly puckered and the six substituents were not interacting with each other and attained pseudo-axial and pseudo-equatorial positions. The photophysical studies in five different solvents indicated that the compounds exhibit large Stokes' shifts unlike reference monomeric BODIPYs indicating that the compounds are promising for fluorescence bioassays. The quantum yields and lifetimes of compounds 1-4 depends on the type of BODIPY unit attached to the cyclotriphosphazene ring.

5,10,15,20-Tetra-2-furylporphyrin.

Mol-ecules of the title macrocycle, C(36)H(22)N(4)O(4), are located on an inversion center. The porphyrin ring shows a wave-like conformation with adjacent pyrrole rings tilted above the porphyrin plane and the inter-porphyrin distance is 3.584 (3) Å. The dihedral angles between the meso-furyl groups and the porphyrin plane are 38.87 (7) and 48.29 (7)°; these are much smaller than those observed for meso-tetra-phenyl-porphyrin, indicating that the meso-furyl groups are more inclined towards the porphyrin plane. The decrease in the dihedral angle is due to the presence of intra-molecular hydro-den bonding between the meso-fury O atom and the ß-pyrrole CH group. Intra-molecular N-H⋯N hydrogen bonds are also present.

Cyclotriphosphazene ring as a platform for multiporphyrin assemblies.

A simple method has been employed to synthesize a cyclotriphosphazene appended with six porphyrins. The reaction of one equivalent of hexachlorocyclotriphosphazene with six equivalents of 5-(4-hydroxyphenyl)-10,15,20-tri(p-tolyl)porphyrin or -21-thiaporphyrin in tetrahydrofuran in the presence of cesium carbonate, followed by simple column-chromatography purification, afforded the hexaporphyrinato cyclotriphosphazene systems as the single products in 80-90 % yields. The metal(II) derivatives (Cu(II), Zn(II)) of the hexaporphyrinato cyclotriphosphazene systems were prepared by treating the hexaporphyrin assemblies with the appropriate metal salts under standard metallation conditions. The compounds are freely soluble in common organic solvents and were characterized by mass spectrometry, NMR, absorption, and fluorescence spectroscopy, and electrochemical techniques. Material studies carried out by using fluorescence microscopy, SEM, and AFM techniques showed that the hexaporphyrinato cyclotriphosphazene systems form ringlike architectures. Preliminary biological studies indicate that the hexacopper(II) porphyrin assembly can be used as an artificial nuclease.

Synthesis of functionalized thia analogues of phlorins and covalently linked phlorin-porphyrin dyads.

The 21,23-dithia and 21-thia analogues of phlorins and mono-functionalized thiaphlorins were synthesized using easily available precursors and the mono-functionalized thiaphlorins were used further to synthesize the first examples of three covalently linked thiaphlorin-porphyrin dyads.

Primary Intraosseous Mucoepidermoid Carcinoma of the Maxilla.

Primary intraosseous mucoepidermoid carcinoma (PIOC) is an infrequent malignancy of the head and neck that exhibits diverse biological behavior. The rareness of the location for a salivary gland tumor and the clinical and radiographic manifestations, suggestive of an odontogenic lesion often pose a diagnostic challenge. We hereby report such a unique case of central mucoepidermoid carcinoma that presented in an ambiguous manner, developing in the maxilla and intruding into the adjacent vital structures, adding a literature review.

Synthesis and crystal structure of 2,3,12,13-tetraalkoxy-21, 23-dithiaporphyrins.

21,23-Dithiaporphyrins with methoxy, butoxy, octyloxy and dodecyloxy substituents at beta-thiophene carbons were synthesised for the first time and the crystal structure of the butoxy derivative indicated that the substituents at the beta-thiophene carbons induce more planarity in the porphyrin ring.

Synthesis, structure and spectral and electrochemical properties of 3-pyrrolyl BODIPY-metal dipyrrin complexes.

The stable dipyrrin substituted 3-pyrrolyl BODIPY (α-dipyrrin 3-pyrrolyl BODIPY) was synthesized by oxidation of dipyrromethane substituted 3-pyrrolyl BODIPY with 2,3-dichloro-5,6-dicyano-benzoquinone in CH2Cl2 at room temperature. The α-dipyrrin 3-pyrrolyl BODIPY is characterized by using HR-MS, 1D, 2D NMR and absorption spectroscopic techniques. The absorption spectrum of α-dipyrrin 3-pyrrolyl BODIPY showed a characteristic absorption band at 630 nm and a charge transfer band at 717 nm due to intramolecular charge transfer from the dipyrrin unit to the 3-pyrrolyl BODIPY unit. The 3-pyrrolyl BODIPY-metal dipyrrin complexes (Pd(ii), Re(i) and Ru(ii)) were prepared by treating α-dipyrrin 3-pyrrolyl BODIPY with appropriate metal salts in toluene-triethylamine at 100 °C and purified by silica gel column chromatography. The crystal structure obtained for the 3-pyrrolyl BODIPY-Pd(ii) dipyrrin complex showed that the 3-pyrrolyl BODIPY and metal dipyrrin moieties are aligned to each other with an angle of 41.9°. The absorption studies showed a strong band at ∼620 nm corresponding to 3-pyrrolyl BODIPY moiety and a weak band at ∼530 nm corresponding to metal dipyrrin unit with complete disappearance of the charge transfer band at 717 nm. The complexes are electron deficient and exhibited only reversible/quasi-reversible reductions in cyclic voltammetry.

Brominated boron dipyrrins: synthesis, structure, spectral and electrochemical properties.

meso-Anisyl boron dipyrrins (BODIPYs) 1-6 containing one to six bromines at the pyrrole carbons have been synthesized by treating meso-anisyl dipyrromethane with 'n' equivalents of N-bromosuccinimide in THF at room temperature followed by oxidation with DDQ, neutralization with triethylamine and further complexation with BF(3)·OEt(2). The brominated compounds were characterized by HR-MS mass, detailed (1)H, (19)F and (11)B NMR and X-ray diffraction studies. The crystal structures solved for compounds 2-6 indicate that the boron dipyrrinato framework comprised two pyrrole rings and one six membered boron containing ring in one plane like other reported BODIPYs. However, the dihedral angle between the BODIPY core and the meso-anisyl group varied from 48° to 88° and the meso-anisyl ring has an almost perpendicular orientation in penta 5 and hexabrominated 6 BODIPYs. The absorption and emission studies showed a bathochromic shift and reached a maximum for tetrabrominated derivative 4, after which there was no change in the peak maxima for penta 5 and hexabrominated 6 derivatives. However, the quantum yields were reduced with the increasing number of bromines. The electrochemical studies revealed that brominated BODIPY compounds 1-6 are easier to reduce compared to unsubstituted meso-anisyl BODIPY 8 and the reduction potential is linearly related to the number of Br groups.