The effect of charge transfer on the polarizability and hyperpolarizabilities of some selected, substituted polythiophenes: a comparative study

Self-stacked small molecules for ultrasensitive, substrate-free Raman imaging in vivo

Raman spectroscopy using surface-enhanced Raman scattering (SERS) nanoprobes represents an ultrasensitive and high-precision technique for in vivo imaging. Clinical translation of SERS nanoprobes has been hampered by biosafety concerns about the metal substrates used to enhance Raman signals. We report a set of small molecules with bis-thienyl-substituted benzobisthiadiazole structures that enhance Raman signal through self-stacking rather than external substrates. In our technique, called stacking-induced charge transfer-enhanced Raman scattering (SICTERS), the self-stacked small molecules form an ordered spatial arrangement that enables three-dimensional charge transfer between neighboring molecules. The Raman scattering cross-section of SICTERS nanoprobes is 1350 times higher than that of conventional SERS gold nanoprobes of similar particle size. SICTERS outperforms SERS in terms of in vivo imaging sensitivity, resolution and depth. SICTERS is capable of noninvasive Raman imaging of blood and lymphatic vasculatures, which has not been achieved by SERS. SICTERS represents an alternative technique to enhance Raman scattering for guiding the design of ultrasensitive substrate-free Raman imaging probes.

Poly(3-alkylthiophene)s show unexpected second-order nonlinear optical response

Poly(3-hexylthiophene)s show upon oligomerization an unexpectedly significant second-order nonlinear optical response.

Structure characterization of molecular complexes for non-linear optical materials I. X-ray analysis and AM1 calculations of 1 : 1 complexes of 8-hydroxiquinoline (1) and isonicotinamide (2) with 2,4,6-trinitrophenol

C6H2N3O7 –·C9H8NO+ (1), Mr = 374.27, P21/c, a = 8.2606(9), b = 9.2574(9), c = 19.906(2) Å, β = 91.441(8)°, Z = 4, R 1 = 0.0405. C6H2N3O7 –·C6H7N2O+, (2), Mr = 351.24, P21/n, a = 14.3064(6), b = 7.4451(7), c = 14.7209(7) Å, β = 116.626(3)°, Z = 4, R 1 = 0.0385. The packing units in both compounds consist of hydrogen bonded cation-anion pairs. The basic first and second-level graph set analysis are given. The (hyper)polarizabilities have been calculated for the crystallographic and optimized molecules, by the semi-empirical quantum method AM1.

Structure characterization of molecular complexes for non-linear optical materials. II. 1 : 1 complexes of 4-methyl-morpholine-N-oxide (1) and 3-picoline-N-oxide (2) with 2,4,6-trinitrophenol, studied by X-ray, AM1 and DFT calculations

(1) C6H2N3O7 – · C5H12NO2 +, Mr = 346.26, P21/c, a = 7.2356(6), b = 10.5765(9), c = 19.593(2) Å, β = 95.101(6)°, V = 1493.5(2) Å3, Z = 4, R 1 = 0.0414; (2) C6H2N3O7 – · C6H8NO+, Mr = 338.24, P21/n, a = 7.8713(5), b = 6.1979(7), c = 28.697(3) Å, β = 90.028(7)°, V = 1400.0(2) Å3, Z = 4, R 1 = 0.0416. The packing units in both compounds consist of hydrogen bonded cation-anion pairs. The (hyper)polarizabilities have been calculated for the crystallographic and optimized molecules, by AM1 and at the DFT/B3LYP(6-31G**) level.