The focus of this review is on host-guest composites with photonic antenna properties. The material generally consists of cylindrical zeolite L crystals the channels of which are filled with dye molecules. The synthesis is based on the fact that molecules can diffuse into individual channels. This means that, under the appropriate conditions, they can also leave the zeolite by the same way. In some cases, however, it is desirable to block their way out by adding a closure molecule. Functionalization of the closure molecules allows tuning of, for example, wettability, refractive index, and chemical reactivity. The supramolecular organization of the dyes inside the channels is a first stage of organization. It allows light harvesting within a certain volume of a dye-loaded nanocrystalline zeolite and radiationless transport to both ends of the cylinder or from the ends to the center. The second stage of organization is the coupling to an external acceptor or donor stopcock fluorophore at the ends of the channels, which can trap or inject electronic excitation energy. The third stage of organization is the coupling to an external device through a stopcock molecule. The wide-ranging tunability of these highly organized materials offers fascinating new possibilities for exploring excitation-energy-transfer phenomena, and challenges for developing new photonic devices.

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We report the preparation and investigation of hierarchically organized host-guest structures, presenting successive ordering from the molecular up to macroscopic scale, thus supporting the relationship between the molecular arrangements and the macroscopic properties. Size, shape and surface composition of the host which is zeolite L play a decisive role. Its base and coat have distinctively different chemical properties. The guests, organic dye molecules or complexes, are well oriented inside the channels and can be organized into distinctive patterns. Zeolite L crystals containing oriented fluorophores in their parallel nanochannels possess remarkable fluorescent properties and they can be arranged in nearly any desired manner by means of self-organization methods. This makes them ideal host-guest structures for the exploitation of energy transfer and energy funneling processes. Size, shape and surface composition of the objects but also the properties of the surface on which they should be organized play a decisive role. We present a simple model of an artificial antenna based on supramolecular organization of dyes in nanochannels of the host, and we explain why zeolite L can be considered as an ideal host for this purpose. The preparation of different dye-zeolite L materials is described, and Förster energy transfer experiments carried out with them. Further, increasing supramolecular organization is discussed: the first unidirectional antenna system on a macroscopic level, organization of crystals and communication of the crystals interior with the environment. Additionally, we explain spectroscopy on monolayers of dye-zeolite L micro-crystals. The materials are shown to be new building blocks for optical, electro-optical and sensing devices.

The orientation of the S 1 r S 0 π,π* transition dipole moments of oxonine (Ox + ), pyronine (Py + ), and POPOP (5,5′-diphenyl-2,2′-p-phenylenebis(oxazole)) in the channels of zeolite L crystals was investigated by means of fluorescence microscopy and single-crystal imaging. Qualitative observations led to the result that the transition moment of POPOP is aligned along the c-axis of the hexagonal crystals whereas the fluorescence of Ox + and Py + is not. More detailed investigations on Ox + showed a cone-shaped distribution of the transition moments with a half-cone angle of 72°. The orientation of the transition dipole moment for all of these molecules is parallel to the molecules' long axis. We found by means of space-filling arguments that POPOP, the van der Waals length of which is about 21 Å, can only be aligned along the channel axis. This is in full agreement with the observed fluorescence anisotropy. For Ox + and Py + , geometrical arguments based on the zeolite L structure give room for only two possible arrangements of the molecules' long axis: a half cone angle of up to 40°for Ox + and up to 30°for Py + , and an angle of about 90°for both of them with respect to the c-axis of zeolite L. The surprising discrepancy between geometrical considerations and the results of the fluorescence measurements can be explained by assuming that Ox + and Py + are exposed to a considerable anisotropic electrical field in the zeolite channels.

Nanochannels have been used as hosts for supramolecular organization for a large variety of guests. The possibilities for building complex structures based on 2D and especially 3D nanochannel hosts are larger than those based on 1D nanochannel hosts. The latter are, however, easier to understand and to control. They still give rise to a rich world of fascinating objects with very distinguished properties. Important changes are observed if the channel diameter becomes smaller than 10 nm. The most advanced guest-nanochannel composites have been synthesized with nanochannels bearing a diameter of about 1 nm. Impressive complexity has been achieved by interfacing these composites with other objects and by assembling them into specific structures. This is explained in detail. Guest-nanochannel composites that absorb all light in the right wavelength range and transfer the electronic excitation energy via FRET to well-positioned acceptors offer a unique potential for developing FRET-sensitized solar cells, luminescent solar concentrators, color-changing media, and devices for sensing in analytical chemistry, biology, and diagnostics. Successful 1D nanochannel hosts for synthesizing guest-host composites have been zeolite-based. Among them the largest variety of guest-zeolite composites with appealing photochemical, photophysical, and optical properties has been prepared by using zeolite L (ZL) as a host. The reasons are the various possibilities for fine tuning the size and morphology of the particles, for inserting neutral molecules and cations, and for preparing rare earth complexes inside by means of the ship-in-a-bottle procedure. An important fact is that the channel entrances of ZL-based composites can be functonalized and completely blocked, if desired, and furthermore that targeted functionalization of the coat is possible. Different degrees of organizational levels and prospects for applications are discussed, with special emphasis on solar energy conversion devices.

The vibrational structure of the highly symmetrical octahydridosilasesquioxane has been investigated in detail, and a harmonic force field in terms of internal force constants has been determined, based on extensive IR and FT-Raman data and on a normal coordinate analysis of H~SisOl2 and DsSigOl2. Group frequencies have been assigned according to a potential energy analysis, and relations to group frequencies of comparable silicon compounds have been discussed. A step by step procedure starting from Oh-H~Sig012 to the frameworks Oh-(-O)8SigO12, D4h-(-0)8Si~012, D4h-(=Si0)8Si8012, and finally to Dw(*0)8T8012, T = Si or A1 and Si/Al = 1, has turned out to be an excellent, enlightening approach for qualitatively and quantitatively describing the vibrational structure of the zeolite A framework. NIR FT-Raman spectra of Na+-exchanged zeolite Y and of Na+-and Ag+-exchanged zeolite A have been measured and compared with each other. An improved force field is reported, and a correlation of the experimental and the calculated IR and Raman spectra of zeolite A has allowed one to assign group frequencies to all fundamental modes. All fundamentals between 11 10 and 950 cm-l belong to antisymmetric T-0-T stretching vibrations while the symmetric T-O-T stretching modes are at 860-830 cm-l, 740-680 cm-l, and 610-570 cm-l. The fundamentals between 490 and 100 cm-l can be described as 0-T-0 bendingvibrations-with the exception of a double four ring and two sodalite cage breathing modes and the 8-ring pore opening-whereas the T-O-T bending vibrations and the torsional modes are below 100 cm-1.

The synthesis and characterization of dye loaded zeolite L sandwiches acting as artificial antenna systems for light harvesting and transport is reported. A set of experimental tools for the preparation of neutral dye-zeolite L materials ranging from low to maximum packing densities has been developed. The role of co-adsorbed water and the distribution of molecules between the inner and the outer surface were found to be the determining parameters. p-Terphenyl (pTP) turned out to be very suitable for studying these and other relevant parameters of neutral dye-zeolite L materials. We observed that pTP located in the channels of zeolite L can reversibly be displaced by water. This can be used when synthesizing such materials. We also observed that all-trans-1,6-diphenyl-1,3,5-hexatriene (DPH) which is very photolabile in solution is stable after insertion into zeolite L. By combining our extensive knowledge of these systems with ionexchange procedures developed in an earlier study, we have realized the first bi-directional three-dye antenna. In this material the near UV absorbing compounds DPH or 1,2-bis-(5-methyl-benzoxazol-2-yl)-ethene (MBOXE) are located in the middle part of zeolite L nanocrystals followed on both sides by pyronine (Py) and then by oxonine (Ox) as acceptors. Fluorescence of the oxonine located at both ends of the cylindrical zeolite L crystals was observed upon excitation of the near UV absorber in the middle section at 353 nm, where neither oxonine nor pyronine absorb a significant amount of the excitation light.

Wir stellen Wirt‐Gast‐Materialien vor, aufgebaut aus zylindrischen Zeolith‐L‐Kristallen, deren Kanäle mit Farbstoffmolekülen gefüllt sind. Die Synthese dieser Stoffe beruht auf der Eigenschaft der Moleküle, in einzelne Kanäle zu diffundieren. Der umgekehrte Prozess, das Herausdiffundieren der Farbstoffe, kann mithilfe eines molekularen “Korkens” unterdrückt werden. Durch Funktionalisierung dieser zapfenförmigen Moleküle lassen sich Eigenschaften wie Benetzbarkeit, Brechungsindex und chemische Reaktivität einstellen. Die supramolekulare Organisation der Farbstoffe innerhalb der Kanäle entspricht einer ersten Organisationsstufe. Damit gelingt es, Licht im Volumen eines Nanokristalls zu sammeln und Anregungsenergie strahlungslos an die Enden des Zylinders oder umgekehrt von dort zur Mitte zu transportieren. Eine zweite Organisationsstufe ist die Kupplung an einen externen Acceptor‐ oder Donor‐Zapfenfluorophor an den Kanalenden, der elektronische Anregungsenergie abfängt oder einspeist. Die dritte, zum Teil noch hypothetische Stufe umfasst die Kupplung an eine externe Funktionseinheit über Zapfenmoleküle. Die Abstimmbarkeit dieser hochorganisierten Materialien bietet attraktive Möglichkeiten zur Untersuchung von elektronischen Energieübertragungsphänomenen und zur Entwicklung von neuen photonischen Funktionseinheiten.