Supramolecular Helical Mesomorphic Polymers. Chiral Induction through H-Bonding Joaquı ´n Barbera ´ , Laura Puig, Pilar Romero, Jose ´ Luis Serrano, and Teresa Sierra* Contribution from the Instituto de Ciencia de Materiales de Arago ´ n, Consejo Superior de InVestigaciones Cientı ´ficas, and Quı ´mica Orga ´ nica, Facultad de Ciencias, UniVersidad de Zaragoza, 50009 Zaragoza, Spain Received June 8, 2004; E-mail: tsierra@unizar.es Abstract: The work described here concerns a challenge of general interest in supramolecular chemistry: the achievement of chiral helical organizations with controlled structures. This work provides a strategy to obtain supramolecular polymers in which a chiral helical conformation has been induced by a noncovalent association, that is, through hydrogen bonding. Polycatenar 2,4,6-triarylamino-1,3,5-triazines, which organize into columnar mesophases and are susceptible to H-bonding interactions, were chosen as a starting point to build up the chiral supramolecular structure. The stacking of these mesogens has been forced to wind in a helical way by means of H-bond association with (R)-3-methyladipic acid, within the mesophase. The optically active columnar organization has been studied in depth by optical microscopy, differential scanning calorimetry (DSC), X-ray diffraction, and circular dichroism. Formation of stable complexes between the triazine units and (R)-3-methyladipic acid has also been investigated by means of NMR diffusion-ordered spectroscopy (DOSY) experiments in chloroform. Introduction The significant role of helical organizations in nature [e.g., R-helical proteins, nucleic acids, tobacco mosaic virus (TMV)] has stimulated the curiosity of researchers in materials chemistry. As an example, the structure of TMV (in which the self- assembly of 2130 polypeptide units gives rise to a columnar organization that is driven to form a helical conformation by interaction with an RNA chain through specific and directional H-bonding interactions) 1 has already been used as a model for synthetic supramolecular columnar organizations prepared from simple molecular units. 2 Furthermore, many appealing research works aimed at building and controlling supramolecular chiral architectures based on helical superstructures have been re- ported. 3,4 Indeed, interesting linear optical 5 and nonlinear optical properties, 6 electrooptical behavior, 7,8 energy transfer, 9 etc., have been found in synthetic helical superstructures, which are often prepared according to the principles of supramolecular chem- istry. 10 In this respect, our research program has been devoted to liquid crystalline organizations and the possibility of achieving helical columnar organizations by π-π stacking of chiral mesogenic molecules synthesized by means of metal coordina- tion. 8,11 In the work described here, we developed a simple strategy based on two types of noncovalent intermolecular interaction, that is, π-π interactions and H-bonding, which enabled the construction of a number of supramolecular liquid crystalline assemblies. 12 Furthermore, since the first chiral helical supramo- lecular polymer was reported by Lehn and co-workers, 13 these types of interaction have been successfully employed as a tool to synthesize supramolecular structures that are capable of adopting chiral helical organizations. 14-17 Our approach consists of merging mesomorphic arrangements based on molecular stacking, which is promoted by π-π (1) Klug, A. 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