The frequency‐doubling of 820nm laser light is one of the properties of a series of nitrocalix‐[4]arenes making them suitable, in principle, for the construction of a blue laser. Derivative 1 is the most promising, since it displays the greatest hyperpolarizability and the largest dipole moment and is stable as a film in a polymer matrix for long periods.

Depolarized hyper Rayleigh scattering of /wtf-nitroaniline {Civ symmetry) and nitrocalix[4]arene (CAV symmetry) in solution has been measured. Using linearly and circularly polarized fundamental radiation information about the ratios between the several hyperpolarizability tensor components, including their sign, was obtained. Results are consistent with the theory developed for both symmetry groups. Comparison between experimental depolarization ratios and ratios obtained from ab initio calculated hyperpolarizability tensor components shows good agreement.

Communications ADVANCED MATERIALSfact, the devices could not be operated in air owing to significant degradation as a function of oxygen and/or water partial pressure. Whereas storage in air hardly changed the I-V characteristic (e.g., 40 % reduction of conductivity after 3 weeks for EC4T) and luminance or output power, operation in air led to a rapid degradation. For example, the output power decayed by a factor of five within 10 s for EC6T and within 20 s for EC7T; EC4T and ECST could not even be measured. Thus, we operated the LEDs in an inert N, atmosphere, which provided relatively stable conditions such that EC7T and EC6T showed little degradation (e.g., 25 Yo) after 15 min of operation at 2 mA. The reason for the rapid degradation in air (and also the slight degradation in a nitrogen atmosphere) is most likely oxidation of the Al electrode, which increases the barrier height and hence reduces the injection probability of electrons. The question remains why different oligothiophenes cause different degradation behavior. At present we can think of two possible answers: a) a different degree of dissociation or follow-up reactions of the oligothiophenes, perhaps at the inner electrode surface, in oxidizing atmosphere and in the presence of a current and/or electric field, and b) different diffusion velocities of 0, and/or H,O through the thin molecular film. The thermal molecular motion induced by the current may be responsible for rapid diffusion in operation while the different film morphologies (see above) may have caused the differences amongst the oligomers. More work is needed to give a clearer answer and to solve the problem of poor LED stability.Finally, we should briefly comment on the output power, which was measured by a calibrated laser power meter and is also displayed in Figure 2 for EC6T (dash-dotted curve, right hand scale). The light emission starts at voltages as low as 2.5 V (for a 160 nm thick EC6T film) and reaches a maximum around 8 V, as can be derived from the inset, which shows the power conversion (not quantum) efficiency curve. This curve varies relatively little (factor of two) as a function of voltage but has only a modest maximum of 4 x YO.(The value for EC7T is even smaller by a factor of four; the value for ECST is markedly higher but could not be measured with sufficient accuracy.) These values have not been corrected for geometric effects, for internal reflection and absorption, and for internal energy conversion processes. If estimated corrections are taken into account the values become considerably higher (by about a factor of 100) and the quantum efficiency may be 1 0~2 -1 0 -3 % . This is still very low and far from being satisfactory, in particular in view of applications. We have some evidence that the low efficiency has various causes, such as film morphology, electrode material with too high a work function, interface bonding and reactions, and the physical properties of the molecules. We believe that it can be improved by orders of magnitude if materials and preparat...

Calix [4]arenes are a novel type of molecules for nonlinear optics. In a single molecule four r-conjugated systems are combined.Corona poled guest-host polymer systems [calix[4]arenes-poly (methyl-methacrylate)]with transparency into the UV and loading up to 100% show a high degree of orientation. The maximum resonant & nonlinear coefficient measured at a fundamental wavelength of 590 nm is 51 pm/V. The dj3 values of the thin films relax after poling to 65% of their maximum value. Results indicate self-organization of the molecules upon poling.Interest in organic molecules for use in nonlinear optics (NLO) is still growing because of their potential use in optical communication, optical switching, frequency conversion, etc. As to this purpose incorporation of organic materials into thin films is necessary. Polymer systems are well suited for thin-film applications. Some basic types of NLO polymer systems are to be distinguished:' (i) Guesthost polymer systems, (ii) Functionalized polymers273 and (iii) Polymer networks.4 The first type is the most easy to prepare but shows some major disadvantages, as poor temporal stability of the molecular orientation after alignment. and poor solubility ( < 10 wt %) of the NLO chromophore in the polymer matrix. Functionalized polymers in which the chromophore is covalently attached to or incorporated in the polymer backbone allow a much larger chromophore concentration. Polymer networks allow only very little molecular mobility and therefore the polar ordering is stable.In this letter first results of second harmonic generation (SHG) in corona poled thin films of newly synthesized calix [4]arenes in poly (methyl-methacrylate ) (PMMA) are presented.In a single calix [4]arene molecule ( Fig. 1) four r-conjugated donor-acceptor systems are combined after functionalization of the phenolic rings.5 The combination of four conjugated units increases the hyperpolarizability (B) of the molecule and is accompanied by a hypsochromic shift of the charge transfer band in the absorption spectrum. The wavelengths of maximum absorption (&,,) and the onset of absorption (&,,,) are compaiable with molecules which have one single r-conjugated system. For the nitrocalix[4]arene derivative, which is investigated, fl,= 1.4X 1O-38 m4/V, &,,,.=291 nm and /z,,,,E=365 nm.' Thin films were prepared by spin coating of nitrocalix [4]arene-PMMA mixtures in chloroform on Pyrex glass and IT0 coated glasses. Typical film thickness was -0.25 ,um. After annealing for 10 min at 90 "C the films were aligned in a corona discharge6,7 ( 10 kV) during 15 min at 110 "C. SHG efliciency was measured using a nanosecond Nd:YAG laser in combination with a dye laser as a source of fundamental radiation. A Soleil-Babinet compensator was used to adjust the polarization of the fundamental beam. The sample was rotated in the laser beam with its rotation axis perpendicular to the incident polarization direction. Separation of fundamental and harmonic radiation was achieved by use of a suitable filter set. Absolute d values we...

darauf schlieDen, daR beide Verbindungen in ihrer Struktur sehr ahnlich sind.Ein Komplex des Typs [OsCl,,] (Y = Heteroatomeinheit), wie er ursprunglich als Produkt der Reaktion von 2 rnit 1 erwartet wurde, ist bei Verwendung des Methyloxycarbonylalkylphosphans 6 erhaltlich. 8 bildet sich nach vierstundigem Erhitzen einer Hexan-Losung von 7['11 und 6 auf 110 "C in einer Ausbeute von 90 % (Schema 3). Mit CO I[ O S C I~( C O ) (~' -P -s ) ( q~-s ) l H 9 10 P -0 = ;PrZPCH2CO2Me (6) Bei den bisher untersuchten Molekulen besteht der ,,NLO-Phor", d. h. die Struktureinheit, die fur die nichtlinearen optischen Eigenschaften verantwortlich ist, aus einem einzigen konjugierten n-Elektronensystem rnit einem oder mehreren Elektronendonoren und/oder -acceptoren (D-n-A-Molekule). Eine Erweiterung des konjugierten n-Elektronensystems