Reactive state selectivity in photodimerization through micellar counter-ion effects: photodimerization of acenaphthylenes

Ramesh, V.; Ramamurthy, V.

doi:10.1016/0047-2670(84)80020-9

Cited by 21 publications

(10 citation statements)

References 15 publications

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“…Enhancements of the reaction rates have been described for cations and tetraphenylporphyrins [109], chlorophylles [110] and for amines with OPA [111]. Photochemical reactions are also modified in the presence of different micellar media [112][113][114][115][116].…”

Section: Properties Leading To Applicationsmentioning

confidence: 99%

Luminescence in organized media and supramolecular interactions:physicochemical aspects and applications

Lerner¹,

Martín²

2000

Analusis

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Introduction Molecular luminescence of analytes in organized media or in supramolecular complexes of cyclodextrinsThe photophysical and photochemical behaviour of molecules complexed to cyclodextrins (CD) is generally different from their behaviour in solution. The first observations in the field were qualitative and were related to the increased stabilisation of labile molecules, mostly drugs, against photodegradation when complexed to natural cyclodextrins [1]. Complexation by CD's was then the preferred subject for those involved in supramolecular chemistry and drug vectorisation techniques [2] as well as in separation techniques [3][4][5]. Stabilization of a molecule against photochemical degradation is still very important in the field of pharmaceutical sciences. A recent example is the stabilisation of promazine as an inclusion complex with β-cyclodextrin [6]. Other photochemists were attracted quite early to this field of research and initiated studies, which were mostly photophysical in nature [7,8]. The key observation was that the formation of supramolecular complexes of analytes with cyclodextrins (CDs) resulted in an increase of their fluorescence quantum yield or even in the appearance of room temperature phosphorescence (RTP) [9][10][11][12]. This enhancement has been used to increase the sensitivity and the selectivity in both luminescence and chromatographic techniques [13-15].We will not say more about RTP with CDs as the subject will be developed in another contribution in the same issue of this Journal. However RTP is also observed in the solubilization of analytes in micellar colloïdal solutions and this field will be reviewed hereunder.These properties have been used to develop analytical techniques, which combine the selectivity of complexation with an enhanced emission [16][17][18][19]. In this way an improvement in the detection limits is obtained in many separation techniques such as HPLC, capillary electrophoresis (CE) or planar chromatography. Furthermore these molecular interactions allow to reveal or to stabilize new molecular forms or to turn species which are normally non-emitting into luminescent ones. All these aspects are reviewed hereunder after a short summary on the nature of the intermolecular interactions, which lie at the heart of these effects. Nature of the interactions between an analyte and a CD or a micelleWithout going into a thorough analysis of the origin of the interactions which exist between molecules in dense media which concern us here, it seems useful to recall the most important factors which should be taken into account when any type of luminescence, fluorescence or phosphorescence is involved.

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Section: Properties Leading To Applicationsmentioning

confidence: 99%

Luminescence in organized media and supramolecular interactions:physicochemical aspects and applications

Lerner¹,

Martín²

2000

Analusis

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“…Previously acenaphthylene photodimerization has been conducted in a number of confined and ordered media such as liquid crystals, micelles, dendrimers, polymers, silica surface, clay, zeolites and Pd-nanocages. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Selectivity obtained in most media (except the Pd-nanocage) is lower than that observed within the octa acid capsule. Selectivity and enhanced reactivity during direct excitation is attributable to the ability of the nanocapsule to localize, preorient and restrict the mobility of the reactant olefins in the short excited singlet state lifetime.…”

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confidence: 99%

Photodimerization of acenaphthylene within a nanocapsule: excited state lifetime dependent dimer selectivity

Kaanumalle

Ramamurthy

2007

Chem. Commun.

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“…In fact the non-radiative decay rate constant (k nr ) of the alkanolamine form enhances in the presence of a CTAB micellar environment (309 ps À1 to 320 ps À1 ). 48,49 The same effect is absent in OBG micelles, as the micellar surface is devoid of any heavy ions. This increment in non-radiative decay channels in CTAB micelles can be rationalized in terms of the heavy atom perturbation effect.…”

Section: Time Resolved Studymentioning

confidence: 97%

“…Similar kinds of enhancement in non-radiative decay pathways are also perceived for many organic compounds in CTAB micellar environments. 48,49 The same effect is absent in OBG micelles, as the micellar surface is devoid of any heavy ions. Therefore, its lifetime increases due to the confinement effect in OBG micellar environments.…”

Section: Time Resolved Studymentioning

confidence: 97%

Fluorescence switching of sanguinarine in micellar environments

Satpathi

Gavvala

Hazra

2015

Phys. Chem. Chem. Phys.

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Sanguinarine (SANG), a key member of the benzylisoquinoline alkaloid family, is well-known for its various therapeutic applications such as antimicrobial, antitumor, anticancer, antifungal and anti-inflammatory etc. Depending on the medium pH, SANG exists in the iminium or alkanolamine form, which emits at 580 nm and 420 nm, respectively. Nucleophilic attack on the C6 carbon atom converts the iminium form to the alkanolamine form of SANG, and these two forms are equally important for the medicinal activities of SANG. To improve its potency as a drug, it is essential to get a physical insight into this conversion process. In this study, we have deployed steady sate and time-resolved spectroscopic techniques to probe this conversion process inside different micellar environments. We have observed that the conversion from the iminium to alkanolamine form takes place in neutral OBG (octyl-β-d-glucopyranoside) and positively charged CTAB micelles, whereas the iminium form exclusively exists in negatively charged SDS micelles. This conversion from the iminium to alkanolamine form in the case of OBG and CTAB micelles may be attributed to the reduced pKa of this conversion process owing to the enhanced hydrophobicity experienced by the iminium form in between the surfactant head groups. On the other hand, the electrostatic attraction between positively charged iminium and negatively charged surfactant head groups stabilizes the iminium form in the stern layer of the SDS micelle. We believe that our observations are useful for selective transportation of any particular form of the drug into the active site. Moreover, loading of any particular form of drug can be easily monitored with the help of fluorescence color switch from orange (iminium) to violet (alkanolamine) without pursuing any sophisticated or complex technique.

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Reactive state selectivity in photodimerization through micellar counter-ion effects: photodimerization of acenaphthylenes

Cited by 21 publications

References 15 publications

Luminescence in organized media and supramolecular interactions:physicochemical aspects and applications

Luminescence in organized media and supramolecular interactions:physicochemical aspects and applications

Photodimerization of acenaphthylene within a nanocapsule: excited state lifetime dependent dimer selectivity

Fluorescence switching of sanguinarine in micellar environments

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