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    A Unified Model: Self-Assembly of Trimesic Acid on Gold
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    Abstract:
    Self-assembly of trimesic acid (TMA) displayed remarkable abundance over its full coverage range on gold under ultrahigh vacuum conditions. Experiments showed that previously well-reported "chicken wire" and "flower" structures were actually two special cases within its full coverage. All observed assembling structures formed hexagonal porous networks that could be well-described by a unified model in which the TMA molecules inside the half unit cells (equilateral triangles) were bound via trimeric hydrogen bonds and all half unit cells were connected to each other via dimeric hydrogen bonds. These porous networks possessed pores of 1.1 ± 0.1 nm in diameter, and the interpore distance was tunable from 1.6 nm on at a step size of ∼0.93 nm. Energetics analysis unveiled that the assembling structures less than one molecular layer was optimally driven by maximization of the dimeric hydrogen bonds.
    Keywords:
    Trimesic acid
    Equilateral triangle
    Five host−guest trimesic-acid-based hydrogen-bonds framework compounds with different guests, namely [(TMA)4·(TMB)3] (1), [(TMA)2·(DMB)1.5] (2), [(TMA)6·(MP)] (3), [(TMA)·(EP)] (4) and [(TMA)·(PP)] (5) (TMA = trimesic acid, TMB = 1,3,5-trimethoxybenzene, DMB = 1,4-dimethoxybenzene, MP = 4-methoxyphenol, EP = 4-ethoxyphenol and PP = 4-propoxyphenol), were obtained through co-crystallization, and were characterized by elemental analysis, infrared spectroscopy analysis, and thermogravimetric analysis. The trimesic acid molecules comprise a hydrogen bonding six-membered cyclic host network that is found in a two-dimensional arrangement in compounds 1 and 2, and in a nine-fold interpenetrated three-dimensional structure in compound 3. In compounds 4 and 5, the trimesic acid and EP/PP molecules form a hydrogen-bonded six-membered cyclic network, resulting in a one-dimensional chain structure through O−H…O hydrogen bonds.
    Trimesic acid
    Thermogravimetric analysis
    Citations (5)
    Nature abhors a vacuum. Attempts to self-assemble nanoporous crystals (clathrates) with trimesic acid and its analogues reveal a striking variability in carboxylic acid motifs that often allow close-packing without clathrate formation. The common R22(8) carboxylic acid dimer is found in tributyl trimesic acid, which forms a "self-filled" two-dimensional chicken-wire network, and in 1, a mimic of trimesic acid dimer 2, which forms a similar network and a cavity clathrate.
    Trimesic acid
    Clathrate hydrate
    Equilateral triangle
    Polygon (computer graphics)
    The characteristics of a hexagonal array formed by seven element hexagonal subarrays are described. It is pointed out that a hexagonal array formed with elements in a grid of equilateral triangles requires fewer elements than with a rectangular arrangement. Dividing a large hexagonal array into contiguous subarrays offers an economic and simpler way of building high-performance phased array antennas. The study of the performance of 3 hexagonal arrays indicates an overall improvement in the sidelobe structure and grating lobe level for one of the configurations considered.< >
    Equilateral triangle
    Hexagonal tiling
    Citations (3)