Electronic spectroscopy of jet-cooled YbNH3

We report the first spectroscopic study of a complex consisting of a rare earth atom in combination with ammonia. Using two-color resonance-enhanced multiphoton ionization (REMPI) spectroscopy, the lowest energy electronic transition of YbNH(3) has been found in the near-infrared. The spectrum arises from a spin-forbidden transition between the (1)A(1) ground electronic state and the lowest (3)E excited electronic state. The transition is metal centered and approximately correlates with the Yb 6s6p (3)P ← 6s(2) (1)S transition. The observation of clear spin-orbit structure in the spectrum confirms the C(3v) symmetry of YbNH(3). Vibrational structure is also observed in the REMPI spectrum, which is dominated by excitation of the Yb-N stretching vibration.     

Facile radical mediated synthesis of azetidin-2,3-diones: potential synthons for biologically active compounds

Abstract  

An operationally simple and efficient approach for the synthesis of azetidin-2,3-diones is described. The starting substrate 2-(2-bromobenzyloxy)ethanoyl chloride was treated with appropriate Schiff’s bases in triethylamine and dichloromethane to afford 3-(2-bromobenzyloxy)azetidin-2-ones. The synthesis of azetidin-2,3-diones was successfully achieved via radical mediated rearrangement of appropriately substituted 3-(2-bromobenzyloxy)azetidin-2-ones using n-tributyltin hydride and AIBN in refluxing dry benzene.     

A Ni2+ selective chemosensor based on partial cone conformation of calix[4]arene

Synthetic strategies are described to synthesize the calix[4]arene diamine 4 of partial cone (paco) conformation, which on condensation with 9-anthracene carbaldehyde forms the chemosensor 5 in paco conformation. The chemosensor 5 undergoes fluorescence enhancement in the presence of Ni(2+) ions.     

Switching and fluorescence signal amplification with metal ions in allosteric systems based on 1, 3-alternate thiacalix[4]crown

New thiacalix[4]crown derivatives 4 and 5 of 1,3-alternate conformation possessing anthracene and quinoline moieties respectively were synthesised and examined for their cation recognition abilities toward different cations by fluorescence spectroscopy. Selective optical recognition with fluorescence amplification was observed for Fe(3+)/K(+) and Hg(2+)/K(+) in chemosensors 4 and 5 respectively. Further it was observed that the formation of 4·Fe(3+) complex triggers the decomplexation of K(+) ion. Similar allosteric behaviour between Hg(2+) and K(+) was observed in chemosensor 5.     

New terphenyl based mercury ensemble for detection of acetate ions in a plasma like system

A new terphenyl based chemosensor 3 has been designed and synthesized. The binding behavior of 3 and its chemosensing ensemble 3-Hg toward various anions (F(-), Cl(-), Br(-), I(-), HSO(4)(-), H(2)PO(4)(-), CH(3)COO(-), NO(3)(-), N(3)(-), SO(4)(2-), SO(3)(2-), and Cr(2)O(7)(2-)) has been investigated by UV-Vis, fluorescence and NMR spectroscopy. Compound 3 shows a sensitivity for both F(-) and CH(3)COO(-) ions among various anions tested, whereas the ensemble 3-Hg shows a better selectivity for CH(3)COO(-) ions. The ensemble is utilized for CH(3)COO(-) recognition in a blood plasma like system.     

Recognition of adenosine monophosphate and H2PO4- using zinc ensemble of new hexaphenylbenzene derivative: potential bioprobe and multichannel keypad system

Zinc ensemble of hexaphenylbenzene derivative 3 exhibits sensitive response toward adenosine monophosphate (AMP) and H(2)PO(4)(-) ions. Further, the application of derivative 3 as a multichannel molecular keypad could be realized in the presence of inputs of Zn(2+) ions, H(2)PO(4)(-) ions, and AMP.     

A charge transfer assisted fluorescent probe for selective detection of hydrogen peroxide among different reactive oxygen species

A charge transfer assisted fluorescent probe is synthesized which undergoes a change in fluorescence emission at two different wavelengths in the presence of hydrogen peroxide.     

Immobilization and nanoscale film structure of bacterial reaction centers on gold

Photosynthetic bacterial reaction centers (BRC) have shown great potential for bioengineering applications. In the present work we demonstrate their preferentially oriented immobilization on top of a mercaptopropionic acid (MPA) self assembled monolayer (SAM) formed on gold screen printed electrodes (Au-SPE). The AFM of the self assembled biofilm reveals formation of nanohole features with the depths of 2.2–2.5 nm, consistent with the thickness of the BRC (~ 3 nm). Thus, BRCs organize into a sub-monolayer film on top of the MPA SAM layer. The square-wave voltammogram of the BRC films exhibits features due to the redox reactions for the bacteriochlorophyll dimer (the strongest), bacteriopheophytin, and the quinones (weak), indicating that the BRCs are more likely immobilized with the dimer side towards the electrode surface. Non-saturating illumination of the BRC film at open circuit conditions leads to a sharp spike of negative current which could be due to the electron acceptance by the oxidized dimer.     

Synthesis and binding studies of novel bisthiacalix[4]arenes with diimime linkages

A series of novel bisthiacalix[4]arenes with diimine linkages of different aromatic or heteroaromatic dialdehydes have been synthesized. The structure of one of the bisthiacalixarene has been analyzed by X-ray crystallography. These molecules quantitatively extract silver ion from aqueous into organic phase under neutral conditions.     

Graphene-gated biochip for the detection of cardiac marker Troponin I

We report lithium ion intercalation mediated efficient exfoliation of graphite to form monolithic graphene sheets which have subsequently been investigated for the development of highly sensitive label-free electrochemical detection platform for cardiac biomarker, Troponin I (cTnI). The spectroscopic and morphological analysis demonstrated the formation of defect free graphene sheets which were successfully employed to fabricate an inter-digited microdevice in a drain-source configuration on a silicon biochip. The graphene gated biochip functionalized with anti-cTnI antibodies used in label free detection of cTnI which exhibited an excellent sensitivity in the picogram range (∼1 pg mL⁻¹) for cTnI without the use of any enzymatic amplification that promises its potential applicability for bio-molecular detection in clinical diagnosis.