Interactions of "organic fluorine" have gained great interest not only in the context of crystal engineering, but also in the systematic design of functional materials. The first part of this tutorial review presents an overview on interactions known by organic fluorine. This involves π-π(F), C-F···H, F···F, C-F···π(F), C-F···π, C-F···M(+), C-F···C=O and anion-π(F) interactions, as well as other halogen bonds. The effect of the exchange of H vs. F is discussed by means of several examples and a short introduction to the young field of "fluorous" chemistry is given. The second part is dedicated to numerous applications of fluorine and fluorous interactions. It is shown how application of fluorination is used to enable a number of reactions, to improve materials properties and even open up new fields of research.

It is shown that molecular electronic circular dichroism (CD) can systematically be investigated by means of adiabatic time-dependent density functional theory (TDDFT). We briefly summarize the theory and outline its extension for the calculation of rotatory strengths. A new, efficient algorithm has been implemented in the TURBOMOLE program package for the present work, making large-scale applications feasible. The study of circular dichroism in helicenes has played a crucial role in the understanding of molecular optical activity. We present the first ab initio simulation of electronic CD spectra of [n]helicenes, n ) 4-7, 12. Substituent effects are considered for the 2,15-dicyano and 2,15-dimethoxy derivates of hexahelicene; experimental CD spectra of these compounds were newly recorded for the present work. The calculations correctly reproduce the most important spectral features and greatly facilitate interpretation. We propose assignments of the lowenergy bands in terms of individual excited states. Changes in the observed spectra depending on the number of rings and substitution patterns are worked out and rationalized. Merits and limitations of TDDFT in chemical applications are discussed.

The properties of cyclic crown ethers are approximated by acyclic neutral ligands (podands), which are compared and contrasted with open-chain bioionophores and acidic chelating agents in this article. Variations of the endo-polarophilicity/exo-lipophilicity balance, complex stability, ion selectivity can often be accomplished more easily, with greater versatility, and at less expense with acyclic polyethers than with their cyclic counterparts; complexation and decomplexation are generally faster in acyclic systems; and the pseudocavity usually has greater conformational flexibility. Acyclic crown ethers and open-chain cryptands stiffened by rigid "terminal groups" containing donor atoms readily form crystalline complexes of alkali and alkaline earth metals. Some open-chain neutral ligands form helical conformations in their crystalline complexes. The observed coordination numbers and geometries are of theoretical interest. Attractive terminal group interactions lead to pseudocyclic species occupying a position intermediate between cyclic and acyclic ligands. It has recently proved possible to isolate crystalline complexes of alkali and alkaline earth metal ions with weakly donating oligo(ethy1ene glycol ethers) and with glycols; such complexes have also been obtained with sugars. Acyclic neutral ligands can serve as simple models of nigericin-type bioionophores and be used analytically in microelectrodes. The recently discovered crystalline stoichiometric complexes formed by some acyclic neutral ligands with guest molecules such as urea, thiourea, and water provide a fresh insight into weak interactions between neutral molecules and for the development of urea receptors

Efficient guest exchange: The organic zeolite analogue TPP⋅x(THF) (x=0.35–0.65) takes up I2 quickly when exposed to iodine vapor. The previously colorless crystals (a) color at the ends (b), and after 1–2 days the iodine has permeated all the way through the crystal (c). The conductivity values of the TPP⋅y(I2) crystals are of the same order as those of elemental I2. TPP=tris(o‐phenylenedioxy)cyclotriphosphazene.