The cover picture shows mesoscopic strands of highly fluorenscent perylene bisimide ± melamine assemblies as visualized by confocal fluorenscence microscopy. This technique does not only provide topological information such as related AFM or STM images, but truly shows the functionality of fluorescent optical networks of the present supramolecular system. The synthesis and structural investigations of the fluorescent mesoscopic superstructures is presented by F. Würthner et al. on p. 3871 ff. The author wishes to thank the BASF AG for kindly covering the costs for the cover picture

OMBD is due to the combination of shape and bonding features of the molecules, together with kinetic factors such as directional hydrogen bonding, and the self-shadowing and self-correcting effects. Not all organic molecules having shapes similar to 1 and 2 can be used to obtain in-plane ordering by oblique OMBD. Long-range ordering was not observed in films of several other stilbene-type dipolar chromophores without sticky ends. [19] This suggests that the bonding feature of 1 and 2 is necessary to achieve the alignment. We believe that our preliminary results [10] and the mechanism proposed here for the growth and alignment will stimulate interests in using supramolecular assemblies based on hydrogen bonding [18,20] for OMBD growth of ordered thin films. Further experimental and theoretical studies, including computer simulation, are necessary to fully understand the origin of the in-plane ordering, and the role of the materials and deposition conditions on the ordering. Such understanding will rationalize material design and processing conditions for the fabrication of oriented organic thin films for advanced applications, such as nonlinear optics and electro-optics.Nature is abundant with functional structures that are organized hierarchically through non-covalent interactions. Introducing functionality is also a main goal in supramolecular chemistry [1] to make use of molecular recognition events for sensor applications, [2] control of transport processes, [3] or electrical and optical devices. [4] Especially for the latter, spontaneous self-assembly could provide a powerful tool to achieve architectural control and functional specificity. The major challenge confronting such a bottom-up approach is how to position predefined functional building blocks in space to optimize complex processes such as energy or charge transport.As electrical and optical functionalities rely on extended conjugated systems, a lot of work has been devoted to p stacking as the major driving force for one-dimensional columnar superstructures. [5] However, the concomitant electronic interactions are not always desired because of substantial and hardly predictable changes of the molecular properties of the chromophores. Moreover, progress toward long-range three-dimensional structures is difficult to realize for these systems because additional non-covalent forces, such as hydrogen bonding or metal±ligand coordination, often cause the formation of insoluble pigments. [6,7] In this paper we report our initial results toward well-defined mesoscopic structures based on a multifunctional perylene chromophore of high photostability, high fluorescence quantum yield, [8] and distinct redox activity. [9] The process of superstructure formation is shown to involve multiple orthogonal intermolecular interactions, appropriate solubilizing substituents, and a solvent of low polarity (Scheme 1).

General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Abstract: A molecular square with dimensions of about 4 nm, incorporating sixteen pyrene chromophores attached to four ditopic bay-functionalized perylene bisimide chromophores, has been synthesized by coordination to four Pt(II) phosphine corner units and fully characterized via NMR spectroscopy and ESI-FTICR mass spectrometry. Steady-state and time-resolved emission as well as femtosecond transient absorption studies reveal the presence of a highly efficient (>90%) and fast photoinduced energy transfer (k en ≈ 5.0 × 10 9 s -1 ) from the pyrene to the perylene bisimide chromophores and a very fast and efficient electron transfer (>94%, ket ≈ 5 × 10 11 up to 43 × 10 11 s -1 ). Spectrotemporal parametrization indicates upper excited-state electron-transfer processes, various energy and electron-transfer pathways, and chromophoric heterogeneity. Temperature-dependent time-resolved emission spectroscopy has shown that the acceptor emission lifetime increases with decreasing temperature from which an electron-transfer barrier is obtained. The extremely fast electron-transfer processes (substantially faster and more efficient than in the free ligand) that are normally only observed in solid materials, together with the closely packed structure of 20 chromophoric units, indicate that we can consider the molecular square as a monodisperse nanoaggregate: a molecularly defined ensemble of chromophores that partly behaves like a solid material.

Large functional molecular squares have been assembled with ditopic perylene bisimide bridging ligands and Pt(II) and Pd(II) phosphine corner units and their optical, electrochemical and spectroelectrochemical properties have been studied.

Tetraaryloxy-substituted diazadibenzoperylene bridging ligands 1a,b were employed in transition metal-directed self-assembly with Pd(II) and Pt(II) phosphane triflates 2a,b which resulted in complex dynamic equilibria between molecular triangles 3a-d and molecular squares 4a-d in solution. Characterization of the equilibria and assignment of the metallacycles was accomplished by (1)H and (31)P[(1)H] NMR spectroscopy in combination with electrospray ionization Fourier transform ion cyclotron mass spectrometry (ESI-FTICR-MS). It was found that the equilibria depend on several factors, such as the metal ion (Pd(2+) or Pt(2+)), the solvent, and the steric demand of the phenoxy substituents of the diazadibenzoperylene ligands 1a,b. Introduction of bulky tert-butyl groups in 1b shifts the equilibrium significantly in the direction of the molecular squares. Molecular dynamics simulations of the triangle and square structures revealed critical steric effects and restricted conformational flexibilities of the phosphane and diazadibenzoperylene ligands that help explain the distinct dynamic behavior observed in variable-temperature NMR studies. Concentration-dependent UV/vis and fluorescence spectroscopy revealed the limited stability of the assemblies and confirmed the reversible nature of the dynamic equilibria.