title: Pyrene Schiff base: photophysics, aggregation induced emission, and antimicrobial properties.
abstract: Pyrene containing Schiff base molecule, namely 4-[(pyren-1-ylmethylene)amino]phenol (KB-1), was successfully synthesized and well characterized by using (1)H, (13)C NMR, FT-IR, and EI-MS spectrometry. UV-visible absorption, steady-state fluorescence, time-resolved fluorescence, and transient absorption spectroscopic techniques have been employed to elucidate the photophysical processes of KB-1. It has been demonstrated that the absorption characteristics of KB-1 have been bathochromatically tuned to the visible region by extending the π-conjugation. The extended π-conjugation is evidently confirmed by DFT calculations and reveals that π→π* transition is the major factor responsible for electronic absorption of KB-1. The photophysical property of KB-1 was carefully examined in different organic solvents at different concentrations and the results show that the fluorescence of this molecule is completely quenched due to photoinduced electron transfer. Intriguingly, the fluorescence intensity of KB-1 increases enormously by the gradual addition of water up to 90% with concomitant increase in fluorescence lifetime. This clearly signifies that this molecule has aggregation-induced emission (AIE) property. The mechanism of AIE of this molecule is suppression of photoinduced electron transfer (PET) due to hydrogen bonding interaction of imine donor with water. A direct evidence of PET process has been presented by using nanosecond transient absorption measurements. Further, KB-1 was successfully used for antimicrobial and bioimaging studies. The antimicrobial studies were carried out through disc diffusion method. KB-1 is used against both Gram-positive (Rhodococcus rhodochrous and Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacterial species and also fungal species (Candida albicans). The result shows KB-1 can act as an excellent antimicrobial agent and as a photolabeling agent. S. aureus, P. aeruginosa, and C. albicans were found to be the most susceptible microorganisms at 1 mM concentration among the bacteria used in the present investigation.
authors.affiliation: National Centre for Ultrafast Processes, University of Madras , Taramani Campus, Chennai 600 113, Tamil Nadu, India.
authors.forename: Arunkumar
authors.initials: A
authors.lastname: Kathiravan
authors.forename: Karuppasamy
authors.initials: K
authors.lastname: Sundaravel
authors.forename: Madhavan
authors.initials: M
authors.lastname: Jaccob
authors.forename: Ganesan
authors.initials: G
authors.lastname: Dhinagaran
authors.forename: Angappan
authors.initials: A
authors.lastname: Rameshkumar
authors.forename: Devanesan
authors.initials: D
authors.lastname: Arul Ananth
authors.forename: Thilagar
authors.initials: T
authors.lastname: Sivasudha
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry / Q000528:radiation effects; D004583:Electrons; D004926:Escherichia coli / Q000187:drug effects; D005453:Fluorescence; D006860:Hydrogen Bonding; D007097:Imines / Q000737:chemistry; D008956:Models, Chemical; D015394:Molecular Structure; D010636:Phenols / Q000737:chemistry* / Q000528:radiation effects; D055668:Photochemical Processes; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D011721:Pyrenes / Q000737:chemistry* / Q000528:radiation effects; D012240:Rhodococcus / Q000187:drug effects; D012545:Schiff Bases / Q000737:chemistry* / Q000528:radiation effects; D012997:Solvents / Q000737:chemistry; D013057:Spectrum Analysis; D013211:Staphylococcus aureus / Q000187:drug effects; D014867:Water / Q000737:chemistry
chemical_list: D000890:Anti-Infective Agents; D007097:Imines; D010636:Phenols; D011721:Pyrenes; D012545:Schiff Bases; D012997:Solvents; D014867:Water; C030984:pyrene