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ABSTRACT: We investigate the physicochemical properties of a novel imidazolium benzospiropyran derivative, SP(Im), in imidazolium based ionic liquids (ILs). SP(Im) was prepared through alkylation of an imidazole to the photoswitchable compound and this derivative was characterised in imidazolium based ILs with increasing chain length to examine the stability of its merocyanine (MC) and spiropyran (SP) forms and compared to standard spiropyran, BSP. The rate of thermal relaxation of the new derivative is found to be about ten times faster than that of BSP as reflected in rates of 13.9 x 10(-3) s(-1) and 1.0 x 10(-3) s(-1) for SP(Im) and BSP, respectively, in [C(6)mIm][NTf(2)]. Since ILs are believed to form nano-structured domains it is proposed that the covalent attachment of the imidazolium side group of SP(Im) fully integrates the photoswitchable moiety into the non-polar region through side-chain association. In contrast, unbound BSP is relatively free to migrate between both polar and non-polar regions and the MC form is more readily stabilised by the IL charge via through space interactions and spontaneous movement to charged nano-domains leading to enhancement of the MC lifetime. At higher concentrations, rheological and transport properties were investigated to determine the impact of covalent attachment of the BSP fragment to an imidazolium cation on the ionic liquid structure. Ionic conductivity was found to decrease by up to 23% for SP(Im) with effects increasing with cation side-chain length. Unlike BSP, the photoswitching of the SP(Im) did not affect conductivity or viscosity values. This may indicate that the mobility of the photoswitchable compound and the resulting disruption of such movement may be critical to the control of this physical property.
Physical Chemistry Chemical Physics 07/2010; 12(26):7009-17. · 3.57 Impact Factor
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ABSTRACT: Synthesis of imidazolium benzospiropyran derivative, SP Im. Compound characterisation using NMR, Thermogravimetric analysis and Differential Scanning Calorimetry
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ABSTRACT: In the crystal structure of the title compound, C(19)H(17)Cl(2)NO, the indoline and benzopyran ring systems are approximately perpendicular to each other. The indoline ring is in an envelope conformation with the spiro C atom as the flap. The N atom of the indoline ring forms a pyramidal environment, the sum of the angles at this atom being 352.46°.
Acta Crystallographica Section E Structure Reports Online 01/2008; 64(Pt 8):o1430-1. · 0.35 Impact Factor
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Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2007; 2007:4096-7.
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ABSTRACT: A neutral 2-site chloride selective compound has been developed (3), based on a 1,3-alternate tetrasubstituted calix[4]arene providing a preorganized supramolecular scaffold. The resultant supramolecular cavity is among the first to combine urea functional groups bridged with single methylene spacers to pyrene moieties. It combines a naturally and synthetically proven H-bonding system with the elegant ratiometric fluorescent signaling properties of an intramolecular pyrene excimer system, triggered by conformational changes upon anion coordination. The excimer emission of 3 is quenched, with a simultaneous rise in the monomer emission solely by the chloride anion among a wide variety of anions tested. 3 has an association constant of 2.4 x 10(4) M(-1) with chloride. The suitability and advantages of ratiometric optical sensor compounds like 3 for use in practical sensor devices is discussed. 3 has an LOD of 8 x 10(-6) M with chloride in acetonitrile-chloroform (95:5 v/v). A dynamic fluorescence study revealed a response time of < 3 s. A recently developed and simple HPLC-based purification method complimented conventional organic work up methods to yield pure product.
Journal of the American Chemical Society 08/2006; 128(26):8607-14. · 9.91 Impact Factor
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ABSTRACT: Switchable materials have tremendous potential for application in sensor development that could be applied to many fields. We are focusing on emerging area of wireless sensor networks due to the potential impact of this concept in society. Spiropyran-based sensors are probably the most studied type of photoswitchable sensing devices. They suffer from many issues but photofatigue, insufficient selectivity and lack of sensitivity are probably the most important characteristics that hinder their wider application. Here, we are address these issues and demonstrate that covalent attachment of modified spiropyran into a polymeric film significantly reduces photodegradation. The observed signal loss after 12th cycle of switching between the spiropyran and merocyanine forms is only about 27% compared to the loss of 57% of the initial signal in an equivalent experiment based on non-immobilized spiropyran. This has enabled us to demonstrate at least five reversible cycles of detection of an ion of interest (in our case H+) with minimal signal loss. Furthermore, we demonstrate that the sensitivity can be increased by incorporation of additional binding groups in the parent spiropyran molecule. Using molecular modelling to calculate the relevant bond lengths as a measure of interaction between MC and H+, the calculated increase of H-bond strength is approximately an order of magnitude for a derivative containing a methoxy group incorporated in the o-position of the parent spiropyran in comparison to the equivalent unsubstituted phenol. This theoretical result was found to correspond very well with experimental observation. As a result, we have increased the sensitivity to H+ by approximately one order of magnitude.
Journal of Photochemistry and Photobiology A: Chemistry.
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ABSTRACT: In the crystal structure of the title compound, C19H17Cl2NO, the indoline and benzopyran ring systems are approximately perpendicular to each other. The indoline ring is in an envelope conformation with the spiro C atom as the flap. The N atom of the indoline ring forms a pyramidal environment, the sum of the angles at this atom being 352.46°.
Alhashimy, Nameer and Müller-Bunz, Helge and Schazmann, Benjamin and Diamond, Dermot (2008) 5',6-Dichloro-1',3',3'-trimethylspiro[2H-1-benzopyran-2,2'-indoline]. Acta Crystallographica Section E, 64 (8). pp. 1430-1431. ISSN 1600-5368.
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ABSTRACT: Novel modified spirooxazines (SOs) with additional chelating groups were synthesised and the crystal
structure of one of these was determined. UV–vis spectroscopic characterization of the photoisomerization
of the SO derivatives shows that the photochromic behaviour is altered with Zn2+ coordination. In
particular, addition of a group as in carboxylic acid 5 to the indole section of the SO increases the lifetime
of the merocyanine Zn 2+ complex by 20-fold compared to the methylated indole 6.
Alhashimy, Nameer and Byrne, Robert and Minkovska, Stela and Diamond, Dermot (2009) Novel synthesis and characterisation of 3,3-dimethyl-50-(2-benzothiazolyl)- spironaphth(indoline-2,30-[3H]naphth[2,1-b] [1,4]oxazine) derivatives. Tetrahedron Letters, 50 (21). pp. 2573-2576. ISSN 0040-4039.
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ABSTRACT: Spiropyran derivatives have been immobilised on the surface of polystyrene microbeads using different
immobilisation strategies. These functionalised polymeric beads can be reversibly switched between the
colourless inactive spiropyran (SP) and highly coloured (purple) active merocyanine (MC) forms using
low power light sources, such as light-emitting diodes (LEDs). A UV LED (375 nm) is used for the SP
/MC conversion, and a white LED (430–760 nm) for the reverse MC/ SP conversion. The
photochromic behaviour of the coated beads has been characterised using different LEDs and
reflection spectroscopy, employing optic fibres and an in-house-designed holder. Investigations into the
metal-ion binding behaviour of the spiropyran-modified microbeads have shown that Cu2+ ions cause
an appreciable colour and spectral change when brought into contact with the beads in the MC form,
suggesting that a significant interaction is occurring. However, the Cu2+ ions can be completely expelled
by photonic-conversion of the beads into the inactive SP form using a white LED. This sequence has
been successfully repeated six times, suggesting that it is possible to cycle through activation of the
functionalised beads from a non-binding to a binding form (SP / MC) using a UV LED, allow
binding with Cu2+ ions to occur, and subsequently, expel the bound ions and regenerate the passive SP
surface using a white LED. Other metals, such as calcium, do not cause any appreciable colour or
spectral change over the same concentration range and in the presence of the same anion (final
concentration 7.1 104 M nitrate salt in ethanol). The system is therefore self-indicating in terms of
whether the active MC or inactive SP forms are present, and whether Cu2+ ions are bound to the MC
form. In principle, therefore, these functionalised beads could form the basis of a photoswitchable
stationary phase for metal ion binding and detection: irradiation of the stationary phase with UV LEDs
causes retention of guest species due to the presence of the MC form, while subsequent exposure to
white LEDs causes release of guest species into the mobile phase
Scarmagnani, Silvia and Walsh, Zarah and Slater, Conor and Alhashimy, Nameer and Macka, Mirek and Paull, Brett and Diamond, Dermot (2008) Polystyrene bead-based system for optical sensing using spiropyran photoswitches. Journal of Material Chemistry, 18 . pp. 5063-5071. ISSN 1364-5501.
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ABSTRACT: Emerging technologies create new application fields but few of them require that we completely rethink our approach in preparation and characterization of sensors. The vision of internet scale wireless sensor networks (WSNs) requires the deployment of enormous numbers of sensors. This necessarily means that the cost of each sensor must be brought down significantly if this vision is to be realized.
An ideal solution for this problem would be a sensor that does not interact with its environment in any way until there is a need for measurement. Upon the measurement, the sensor’s surface is completely regenerated and returned into the state as before the measurement. This step is critical as it ensures that the measurement did not any effect on the sensor hence no calibration is necessary.
In our work, we use compounds that indeed can be switched between the active and passive state using light. Most commonly used compounds are so called spiropyrans (SP) and spirooxazines (SO). Here we show the recent advance in preparation of reversible, light-modulated sensors using surface immobilised SP/SO derivatives. A further attractive property of these materials is that they are inherently self-indicating through striking colour changes that enable the state to be easily determined (active vs. passive), and the presence of a bound guest to be detected. These spectral changes enable a range of self-diagnostic tests to be incorporated that enable binding events to be controlled at the surface interface, and for real binding events to be distinguished from artefacts arsing from changes in light intensity, or photobleaching of the active component. We have identified most notable problems for utilization of these compounds in “calibrationless” sensors such as relatively weak binding constants, photodegradation, and unfavourable kinetics of switching between the active and passive state and we demonstrate our approach in solving these problems.
Radu, Aleksandar and Kavanagh, Andrew and Scarmagnani, Silvia and Byrne, Robert and Alhashimy, Nameer and Slater, Conor and Diamond, Dermot (2009) Light-modulated ion binding: towards calibrationless sensors. In: PITTCON 2009 - 60th Pittsburg Conference on Analytical Chemistry and Applied Spectroscopy, 8-13 March 2009, Chicago, USA.
