Subhasis Panja

Excited state photodynamics of 4-N,N-dimethylamino cinnamaldehyde: A solvent dependent competition of TICT and intermolecular hydrogen bonding

Abstract This paper describes the dual fluorescence of 4-N,N-dimethylamino cinnamaldehyde (DMACA) in various solvents. Based on major findings the first fluorescence band has been assigned to be arising out of delocalized excited state (DE) and the anomalous fluorescence band in polar aprotic solvents has been assigned to twisted intramolecular charge transfer (TICT) state whereas, in protic solvent it is arising out due to hydrogen bonding interaction between hydrogen donor part of the solvent and carbonyl group of the probe molecule. This hydrogen bonding being an efficient fluorescence quenching channel trammels the TICT formation and thus an apparent competition exists between TICT and hydrogen bonding formation in protic solvent. The calculated absorption spectrum generated from CNDO calculations follows nicely the experimental absorption band. The AM1 calculations corroborate the large dipole moment change and the charge transfer in orthogonal position as found from experimental observations.

Modulation of photophysics due to orientational selectivity of 4-N,N-dimethylamino cinnamaldehyde β-cyclodextrin inclusion complex in different solvents

Abstract This paper delineates some results on the twisted intramolecular charge transfer (TICT) dynamics of 4- N , N -dimethylamino cinnamaldehyde (DMACA) encapsulated in β-cyclodextrin in aqueous and non-aqueous solvents at room temperature. 4- N , N -Dimethylamino cinnamaldehyde is found to form a 1:1 inclusion complex with β-CD in both aqueous and non-aqueous solvents with a binding constant higher in aqueous solvent. The most important feature of the inclusion complexes of 4- N , N -dimethylamino cinnamaldehyde, as revealed from photophysics of normal and twisted intramolecular charge transfer bands, is that there is a preferential orientation of 4- N , N -dimethylamino cinnamaldehyde inside β-CD cavity in aqueous solvent with dimethyl group sticking outside and in non-aqueous solvents it is just the opposite.

Dynamics of twisted intramolecular charge transfer process of 4-N,N-dimethylaminocinnamic acid in α-cyclodextrin environment

This Letter reports some interesting results on twisted intramolecular charge transfer emission of 4-N,N-dimethylaminocinnamic acid complexed with α-cyclodextrin. Salient features of this investigation, as revealed from twisted intramolecular charge transfer emission intensity and position dependence on α-CD concentration, are the formation of 1:2 barrel-shaped complex in addition to 1:1complex, while twisted intramolecular charge transfer (TICT) band intensity shows an increase and then a sharp decrease (bell-shaped variation) along with blue shift and initial addition of base to the solution obstructs the formation of 1:2 complex.

Exploring the location and orientation of 4-(N, N-dimethylamino) cinnamaldehyde in anionic, cationic and non-ionic micelles

Abstract This Letter reports probing of non-ionic, anionic and cationic micelles utilizing different dual emission properties of 4-(N,N-dimethylamino) cinnamaldehyde. Twisted intramolecular charge transfer (TICT) band is more enhanced and blue shifted in non-ionic micelle than those are in ionic micelles. In non-ionic micelle, the molecule enters in the core region whereas, in ionic micelles, it is anchored in the interfacial region with different orientations. Micellar–water interface electric field in ionic micelles was found to have profound effect on TICT decay time. Interestingly, inorganic salt-counterion binding helps the acceptor moiety to enter into the core region in anionic micelle.

Photophysics of 4-(N, N-dimethylamino)cinnamaldehyde/α-cyclodextrin inclusion complex

This paper reports the probing of α-cyclodextrin (α-CD) cavities with the help of dual emission properties of 4-N,N dimethylamino cinnamaldehyde (DMACA) in aqueous solution. An interesting feature could be observed that due to 1:1 complexation DMACA is encapsulated within α-CD in two distinctly different types of orientation as revealed from the relative positions and the intensity of locally excited state localized within donor and acceptor subunits (LE) and twisted intramolecular charge transfer (TICT) bands. In one situation the dimethylamino group is directed towards the larger rim of the cavity and in other the orientation is just the opposite. The different types of complexes were found to be excited selectively in different wavelength regions.

Observation of photoluminescence in a chromophore at room temperature and 77 K

Abstract A moderately air stable Cu I ( amino N ) 2 ( imino N ) 2 chromophore having a Cu(II/I) potential of 0.12 V vs SCE is isolated using a tetradentate N-donor ligand and characterised structurally by X-ray crystallography. It is found to be photoluminescent in fluid solution at room temperature as well as in frozen solution at 77 K.

Photophysics of 4-N,N-dimethylamino cinnamaldehyde in AOT reverse micelles and exploration of its position and orientation

Abstract An attempt has been made in this Letter to locate the position and orientation of 4- N , N -dimethylamino cinnamaldehyde (DMACA) inside sodium bis(2-ethylhexyl) sulfosuccinate (AOT)– n -heptane reverse micelle based on change in photophysical properties of DMACA compared to that in n -heptane. It has been proposed that the possibility of finding the donor moiety inside the small water pool of reverse micelle is maximum while the acceptor group straddles in the remaining part of the reverse micelle. The micropolarity in the vicinity of the donor moiety has been computed in terms of dielectric constant with varying water pool size.

New 1:1:1 complex with N-phenyl pyrrole and nano-cavities

Abstract Interesting patterns of complexation of N -phenyl pyrrole (PPR) with α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) separately and also in binary mixture of both types of cyclodextrins in aqueous solution are reported. PPR forms only one type of 1:1 complex with α-CD with pyrrole group inside the cavity. In β-CD two types of 1:1 complexes with opposite orientations were found to occur and estimation of such complexes has been made by simple new method. A new 1:1:1 complex (α-CDxa0·xa0PPRxa0·xa0β-CD) was observed for the first time. Bigger cavity seems to play a role in binary and ternary complexation.