Muhammad Moazzam Naseer

The boundary layer flow of Casson nanofluid over a vertical exponentially stretching cylinder

In this paper, an analysis is carried out for the similarity solution of the steady boundary layer flow and heat transfer of a Casson nanofluid flowing over a vertical cylinder which is stretching exponentially along its radial direction. Using boundary layer approach and suitable similarity transformation the governing partial differential equations with the boundary conditions are reduced to a system of nonlinear ordinary differential equations. The resulting system is solved with the help of numerical technique, the Runge–Kutta Fehlberg method. The effects of important parameters such as Reynolds number, Prandtl number, Lewis number and the natural convection parameter are described through graphs.

Synthesis and functionalization of heteroatom-bridged bicyclocalixaromatics, large molecular triangular prisms with electron-rich and -deficient aromatic interiors.

The synthesis and functionalization of oxygen and nitrogen atom bridged bicyclocalixaromatics of triangular prism structures are reported. By means of a fragment coupling approach, molecular triangular prisms of electron-rich and electron-deficient aromatic interiors were prepared using 1,3,5-tri(p-hydroxyphenyl)benzene and 2,4,6-tri(p-aminophenyl)triazine as base units and chlorotriazines as pillars. Aromatic nucleophilic substitution reaction of chlorotriazine moieties with functionalized amines led to triangular prisms with functionalizations on the peripheral edge positions, while functionalized triangular prisms on the vertex nitrogen positions were obtained using 2,4,6-tri[(p-allylamino)phenyl]triazine derivative as a starting material. Symmetrical and distorted molecular triangular prisms in the solid state were revealed by X-ray crystallography. As evidenced by NMR spectroscopic data, however, all cage molecules synthesized most probably adopted highly symmetric triangular prism structures in solution phase. The functionalized shape-persistent triangular prism structures might find applications in molecular recognition and in the construction of higher and more sophisticated molecular architectures in supramolecular chemistry.

In-vitro antibacterial, antifungal and cytotoxic properties of metal-based furanyl derived sulfonamides

A new series of antibacterial and antifungal furanyl-derived sulfonamides and their cobalt (II), copper (II), nickel (II) and zinc (II) metal complexes have been synthesized, characterized and screened for their in-vitro antibacterial activity against four Gram-negative (Escherichia coli, Shigella flexneri, Pseudomonas aeruginosa and Salmonella typhi) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacterial strains and, for in-vitro antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glaberata. The results of these studies revealed that all compounds showed significant to moderate antibacterial activity. However, the zinc (II) complexes were found to be comparatively much more active as compared to the others. For antifungal activity generally, compounds (22) and (24) showed significant activity against Escherichia coli (a), (6) against Shigella flexeneri (b), (16) and (22) against Pseudomonas aeruginosa (c), (14) and (16) against Salmonella typhi (d), (9) against Staphylococcus aureus (e) and, (14) and (16) against Bacillus subtilis (f) fungal strains. The brine shrimp (Artemia salina) bioassay was also carried out to study their in-vitro cytotoxic properties. Only three compounds, (6), (10) and (23) displayed potent cytotoxic activity with LD50 = 1.8535 × 10− 4, 1.8173 × 10− 4 and 1.9291 × 10− 4 respectively.

Antibacterial, antifungal and cytotoxic properties of some sulfonamide-derived chromones

A series of antibacterial and antifungal sulfonamide (sulfanilamide, sulfaguanidine, sulfamethaxozole, 4-aminoethylbenzenesulfonamide and 4-amino-6-trifluoromethyl-benzene-1,3-disulfonamide) derived chromones, previously reported as inhibitors of carbonic anhydrase, have been screened for in-vitro antibacterial activity against four Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi and Shigella flexeneri) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacterial strains, and for in-vitro antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani, Candida glaberata. All compounds (1)–(5) showed significant antibacterial activity against all four Gram-negative species and both Gram-positive species. However, three of them, (1), (4) and (5), were found to be comparatively much more active compared to (2) and (3). Of these, (5) was found to be the most active one. For antifungal activity, generally compounds (1) and (2) showed significant activity against more than three strains whereas (3)–(5) also showed significant activity against varied fungal strains. In the brine shrimp bioassay for in-vitro cytotoxic properties, only two compounds, (4) and (5) displayed potent cytotoxic activity, LD50 = 2.732 × 10− 4 M) and LD50 = 2.290 × 10− 4 M) respectively, against Artemia salina.

Synthesis, spectral characterization, self-assembly and biological studies of N-acyl-2-pyrazolines bearing long alkoxy side chains

A series of new pyrazoline derivatives (1b-4c) bearing N-acyl arms and nine to twelve carbon long alkoxy side chains was synthesized and characterized on the basis of spectroscopic data and microanalysis. The nature of self-assembly to understand the interplay of alkoxy chain crystallization and various supramolecular interactions was investigated using single crystal X-ray diffraction studies. Interesting self-assembled supramolecular structures of 1b and 4c were observed in the crystal lattice owing to various CH⋯O, H⋯H, CH⋯π, lonepair⋯π and π⋯π interactions. Further, all the synthesized compounds (1b-4c) were screened for their in vitro antifungal and anti-inflammatory activities. Compounds 2b, 3b, 2c and 3c showed significant to moderate antifungal activity against Microsporum canis whereas most of the other compounds were found inactive against all the five tested fungal strains. Good anti-inflammatory activity was observed for compounds 1b with IC50 value 331 μM compared to 273 μM for Indomethacine, a standard reference drug. The bio-activity data demonstrates the relationship between lipophilicity, solubility and bioavailability.

Homologous 1,3,5-triarylpyrazolines: synthesis, CH⋯π interactions guided self-assembly and effect of alkyloxy chain length on DNA binding properties

A series of new 2-pyrazoline derivatives (1c–12c) bearing one to twelve carbon homologous alkyloxy side chains have been synthesized in good to excellent yields via intramolecular cyclization reaction on treatment of chalcone intermediates (1a–12a) with phenyl hydrazine (1b) and characterized on the basis of their physical and spectral (IR, 1H & 13C NMR, GC-MS) data. The solid state structure of compound (2c) showed intriguing and unique 1D-supramolecular zigzag chain-like self-assembled structure, the driving force of which is only CH⋯π interactions. DNA interaction studies have also been carried out on selected compounds 1c, 3c, 5c, 6c, 9c and 12c of the series by UV-visible spectroscopy to evaluate their anticancer potential and the effect of alkyloxy chain length on DNA binding property. All the tested compounds showed strong DNA binding (105–106 M−1 binding constants) with hyperchromic effect. A slight increase in the DNA binding strength, observed on increasing the chain length of alkyloxy groups, was attributed to their conformational arrangements, leading to the best fit conformation of 1,3,5-triaryl moiety in the minor groove of DNA structure.

Layer-by-layer assembly of supramolecular hexagonal blocks driven by CH–π and π–π interactions

A unique layer-by-layer assembly of hydrogen bond-directed hexagonal blocks, consisting of 2,4,6-trimethoxy-1,3,5-triazine and 1,3,5-tris(p-hydoxyphenyl)benzene as building units, was constructed in the solid state. The adjacent layers of the assembly interact through various CH–π and π–π stacking interactions.

Robustness of thioamide dimer synthon, carbon bonding and thioamide–thioamide stacking in ferrocene-based thiosemicarbazones

The role of thioureas in crystal engineering as robust supramolecular synthons is now recognized, but their analogs, namely thiosemicarbazones/N-iminothioureas, have not received the attention they deserve. A series of five structurally related ferrocene-based thiosemicarbazones 1–5 have been designed, synthesized and crystallographically characterized in order to investigate the prevalence of the thioamide dimer synthon and carbon bonding. All of the compounds have shown a general preference for the adoption of the cis, trans conformation about the central thiourea moiety which is ideal for the formation of a dimeric hydrogen-bonded R22(8) {⋯H–N–CS}2 synthon as the building block. Therefore, this dimeric synthon is observed in all of the compounds, with the methyl group particularly set for playing its supportive stabilization role through C–H⋯S and carbon bonding interactions. Carbon bonding has been observed in all of the compounds except compound 2. The centrosymmetrically arranged thioamide protons present in trans conformation through N–H⋯H–C interactions give rise to the formation of tapes of varying topology in all of the compounds except 3, where a staircase arrangement of dimeric molecules is observed. Another notable feature of the crystal packing of 1–5 is the presence of thioamide–thioamide stacking, which has been observed in all five compounds. The prevalence of the thioamide dimer synthon, carbon bonding, and observation of new thioamide–thioamide stacking interactions indicate a much larger role for this class of compounds as a design element in crystal engineering than anticipated so far.

Synthesis and spectral characterization of new homologous 1,3,5-triaryl-2-pyrazolines: Influence of alkyloxy chain length on fluorescence.

Twelve new homologous 1,3,5-triaryl-2-pyrazolines (1c-12c) have been synthesized and characterized on the basis of their spectral (IR, (1)H and (13)C NMR and MS) data and microanalysis. The influence of alkyloxy chain length on absorption and fluorescence properties of 1c-12c was studied by UV-Vis and emission spectroscopy. For all the compounds, fluorescence was observed in the blue region of the visible spectrum. Furthermore, a strong influence of alkyloxy chain length was found on the emission intensity of 1,3,5-triaryl-2-pyrazolines, without causing any major blue- or red-shift in the emission wavelength (λmax(em)). The absorption and emission maxima (λmax(abs) and λmax(em)) for all the compounds were observed in the range of 408-416nm and 471-476nm, respectively. The effect of chloro-substituent present on the conjugated backbone of 1,3,5-triaryl-2-pyrazoline moiety is also discussed.

Structure-fluorescence relationship: interplay of non-covalent interactions in homologous 1,3,5-triaryl-2-pyrazolines

Fluorescence intensity depends on the synergy of multiple non-covalent interactions in solutions. Twelve new homologous 1,3,5-triaryl-2-pyrazolines (1–12)·Br have been synthesized and characterized on the basis of their spectral (IR, 1H and 13C NMR and MS) and microanalytical data to investigate the interplay of non-covalent interactions and their effect on absorption and fluorescence properties by UV-vis and emission spectroscopies. All the compounds showed fluorescence in the blue region of the visible spectrum, but a strong influence of alkyloxy chain length was observed on the emission intensity without causing any major blue- or red-shifts in the emission wavelengths. The absorption and emission maxima (λabsmax and λemmax) for all the compounds were observed in the range of 404–414 nm and 467–479 nm, respectively. Compound 12·Br showed the maximum emission intensity, indicating the dominant role of weak van der Waals forces in driving the solution state self-assembly in comparison to other relatively strong intermolecular interactions. The influence of different halogen substituents present on the conjugated backbone of the 1,3,5-triaryl-2-pyrazoline skeleton in relation to the increasing alkyloxy chain length and their ultimate role in driving the solution state self-assembly and fluorescence properties are also discussed.