Inamur Rahaman Laskar

A 1D thiocyanato bridge nickel(II) system: crystal structure and magnetic property

Abstract A one-dimensional coordination polymer of nickel(II), [(μN,S-NCS)2{Ni(ampy)}]n (ampy=1-(2-aminoethyl)pyrrolidine) has been synthesized and characterized by X-ray single crystal analysis. Structure analysis reveals that each nickel(II) center is coordinated in a distorted octahedral fashion with four bridging thiocyanato ligands and one mesocyclic diamine ligand. The low temperature (300–18 K) magnetic measurement shows that the system is ferromagnetically coupled. The magnetic data are fitted to the de Neef equation, giving the parameters J=1.4 cm−1 and g=2.08.

Facile tuning of the aggregation-induced emission wavelength in a common framework of a cyclometalated iridium(III) complex: micellar encapsulated probe in cellular imaging

A simple synthetic protocol involving two steps was developed for the syntheses of a series of monocyclometalated iridium(III) complexes. Initially, an intermediate, [IrHCl[(o-C6H3X)P(Ar)x−(PArxRy)2] [A (i, j, k, l)], six-coordinated iridium(III) complex involving a 4-membered chelate was isolated. Then, it was transformed into a monocyclometalated iridium(III) complex, [(C^N)Ir(PArx−1Ry)2(Cl(H)] (1–12), by the replacement of the 4-membered chelates with 5-membered cyclometalates. The intermediates and the complexes were structurally characterized by FTIR, 1H, 13C and 31P NMR spectroscopies. Octahedral coordination for Ir(III) in 2, 8 and 9 was established by single crystal X-ray diffraction. Photo-physical experiments and quantum chemical calculations revealed a mixed LC/MLCT/LLCT nature for the lowest excited states of all these complexes that emit bright light in the solid state. Fine tuning of the emission wavelength throughout the visible range was achieved by suitable combinations of chromophoric cyclometalates and non-chromophoric aryl phosphine ligands. More interestingly, all the studied complexes were found to be aggregation-induced emission (AIE) active. One of these AIE active materials (6) was encapsulated inside polymeric micelles that inhibit the macroscopic precipitation of the aggregated complex, <200 nm water-soluble particle exhibiting a strong emission. These colloidal luminescent particles were used as a potential non-toxic bio-imaging probe.

Highly sensitive explosive sensing by “aggregation induced phosphorescence” active cyclometalated iridium(III) complexes

Two phosphorescent complexes [Ir(o-CHOppy)(PPh3)2(H)Cl] (1) and [Ir(ppy)(PPh3)2(H)Cl] (2) exhibiting ‘aggregation induced phosphorescent emission (AIPE)’ properties have been found to be very sensitive to the detection of picric acid (PA). The detection limit for PA has been checked and was found to be 264 nM and 65 nM for complexes 1 and 2, respectively.

Rare observation of ‘aggregation induced emission’ in cyclometalated platinum(II) complexes and their biological activities

Three strong solid state emissive cyclometalated platinum(II) complexes [Pt(C⁁N) (CH⁁N) (Cl)] (1) (C⁁N/CH⁁N = 2-phenylpyridine, C⁁N = bidentate and CH⁁N = monodentate), [Pt(C⁁N) (P⁁P)]Cl [P⁁P = bis(diphenylphosphino)ethane (2) and cis-1,2-bis(diphenylphosphino)ethene (3)] were reported. These were identified as ‘Aggregation Induced Emission (AIE)’ active complexes based on controlled experiments. Cytotoxicity and cell imaging have been studied for the complex 2.

Cis–trans isomerism in nickel(II)–diamine nitrite: synthesis and single crystal structure of an unusual cis-dinitronickel(II) complex, [NiL2(NO2)2] (L=1,2-diamino-2-methylpropane)

Abstract The complexes [NiL3](NO2)2·2H2O (violet, 1) and cis-[NiL2(NO2)2]·0.5H2O (pink, 1b) (L=1,2-diamino-2-methylpropane) have been synthesized from solution. The X-ray single crystal structure analysis of compound 1b has been carried out, but the presence of a water molecule cannot be detected. Upon heating, complex 1b undergoes dehydration followed by an endothermic phase transition to produce trans-[NiL2(NO2)2] (1d). The violet species (1) also undergoes dehydration upon heating with deamination resulting (1d).

‘Aggregation induced emission’ active iridium(III) complexes with applications in mitochondrial staining

Two new bis-cyclometalated iridium(III) complexes, [Ir(F2ppy)2(L)] and [Ir(ppy)2(L)], where F2ppy = 2-(2′,4′-difluoro)phenylpyridine, ppy = 2-phenylpyridine and L = 1,2-((pyridin-2-ylimino)methyl)phenol, have been designed and synthesized by a convenient route. We have univocally characterized their structure by 1H NMR, 19F NMR, HRMS and SXRD. Both complexes exhibit strong ‘Aggregation Induced Emission (AIE)’ activity, which has been investigated using spectroscopy measurements, ab initio quantum chemical calculations and by analysing their crystal packing. One of the complexes has been shown to have a potential application as a non-toxic bio-imaging probe for mitochondrial staining.

Synthesis and characterization of cis and trans isomers of [NiL2(NCS)2] [L=1-(2-aminoethyl)pyrrolidine]: X-ray single-crystal structures

Abstract The isomeric complexes trans-[NiL2(NCS)2] (violet) (1) and cis-[NiL2(NCS)2] (blue) (2) [L=1-(2-aminoethyl)pyrrolidine] have been synthesized, varying solvents and temperature, and their X-ray crystal structures have been determined. Both the isomers possess the same space group, P21/c, having distorted octahedral geometry.

Simple ratiometric push–pull with an ‘aggregation induced enhanced emission’ active pyrene derivative: a multifunctional and highly sensitive fluorescent sensor

A simple ratiometric push–pull and ‘aggregation-induced emission enhancement (AIEE)’ active pyrene based compound, 2-(pyren-1-yl)pyridine (L), was synthesized and characterized by 1H NMR, HRMS and SXRD. The synthesized compound was established as a highly selective and sensitive multi-functional sensor that exhibits a ratiometric fluorescent response, detecting picric acid, H+ and Al3+ [observed sensitivity: 56 nM (12.82 ppb) for picric acid; 2.4 nM (0.27 ppb) for trifluroacetic acid; 2.3 nM (0.86 ppb) for Al3+]. Both L and LH+ have shown emission tuning ability on varying their concentration in solution. Computational calculations (DFT and TD-DFT) have been correlated with the experimental spectroscopic properties.

Synthesis of an aggregation-induced emission (AIE) active salicylaldehyde based Schiff base: study of mechanoluminescence and sensitive Zn(II) sensing

Syntheses of multi-functional Aggregation-Induced Emission (AIE) active molecules in a simple manner have been drawing great attention in current luminescence materials research. In this report a simple diamine molecule (N1-tritylethane-1,2-diamine(1)) is reacted with salicylaldehyde using a Schiff-base technique which results in a new AIE active organic molecule [2-((2-(tritylamino)ethylideneamino)methyl)phenol (2)]. Computational calculations support that the nature of the transition is intra-molecular charge transfer/twisted intramolecular charge transfer (ICT/TICT). The mechanism of AIE has been attributed to restricted intramolecular rotation (RIR). Packing diagrams support that the nature of the aggregation is J-aggregation. The compound, 2, exhibits an irreversible mechanoluminescence (ML) property with a drastic colour change from blue to green (λmax, 445 nm → 512 nm) upon grinding. However, it undergoes a reversible transition with the same colour change (blue → green) through applying pressure axially (using a hydraulic press). The reversible transition is observed by lowering the temperature of 2 to that of liquid nitrogen. The causes of such transitions showing variations in the emission colour upon different triggers have been investigated. In addition, 2 has been successfully tested for the sensing of Zn(II) and shows a rare turn-on luminescence change, the mechanism behind which has been explored. The detection limit for Zn(II) is determined to be 0.064 ppm.

Dual emission and multi-stimuli-response in iridium(III) complexes with aggregation-induced enhanced emission: applications for quantitative CO2 detection

Four new Ir(III) complexes with the general formula [IrHCl(C^N)(PPh3)2] containing different conjugated Schiff base ligands (C^N) have been synthesized and characterized by 1H, 13C, and 31P NMR, HRMS, and IR spectra and one of them by single crystal X-ray diffraction. Their photophysical properties in solution and in the solid state have been analyzed and three main practical results have been obtained: (i) a dual fluorescent and phosphorescent emissive complex in solution, (ii) successful acid/base sensing in the solid state and (iii) quantitative CO2 detection. Quantum chemical calculations have been employed to assign the character of the lowest excited states. A plausible explanation for the observed aggregation induced enhanced emission (AIEE) is given, based on the restriction of intramolecular motions due to the effect of intermolecular C–H⋯π and C–H⋯Cl type interactions upon aggregation.