Molecular ribbons (MRs), one-dimentional topological polycyclic aromatic hydrocarbons (PAHs), are of importance for synthetic chemistry and material sciences. Herein, we disclose an effective strategy to develop boron-doped MRs, i.e. photochemical cyclization on conjugated organoboranes for rapid π-extension. A series of ribbon-type boron-doped PAHs that own multiple cove edges were synthesized using Mallory photoreaction in solution. Two of them feature isomeric C 68 B 2 π-skeletons with 2.2 nm in length, thus representing a new kind of boron-doped MRs. The boron atoms endow them with sufficient Lewis acidity, and notably, the formed Lewis acid-base adducts based on borondoped MRs display the photo-induced dual-dissociation behavior in the excited state and thus photochromism property. Moreover, despite of the highly contorted topological conformations, their potential utility as organic semiconductor was demonstrated by fabrication of organic field-effect transistors.

Units of ureidopyrimidinone (UPy) which dimerize via strong quadruple hydrogen bonding are widely used for the construction of supramolecular systems. This self-complementary system exists in the tautomerism equilibrium of 4­[1H]-pyrimidinone dimer and pyrimidin-4-ol dimer, making generated supramolecular assembly systems essentially complicated. In this contribution, a rational but simple design concept is described for preorganizing the self-complementary quadruple hydrogen bonding of UPy via supramolecular strategy into a single-quadruple DDAA-AADD dimeric array. With this concept, the designed UPy derivatives form only 4­[1H]-pyrimidinone dimer with a ketone configuration via intermolecular hydrogen-bonding interactions, both in the solid state as well as in solution, as is evident from single-crystal X-ray diffraction and 1H NMR spectroscopy. The single DDAA-AADD dimeric array provides defined noncovalent driving forces that can be used to generate constitutionally clear supramolecular structures that are vitally important in the fields of supramolecular chemistry and materials.

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Molecular ribbons (MRs), one-dimentional topological polycyclic aromatic hydrocarbons (PAHs), are of importance for synthetic chemistry and material sciences. Herein, we disclose an effective strategy to develop boron-doped MRs, i.e. photochemical cyclization on conjugated organoboranes for rapid π-extension. A series of ribbon-type boron-doped PAHs that own multiple cove edges were synthesized using Mallory photoreaction in solution. Two of them feature isomeric C 68 B 2 π-skeletons with 2.2 nm in length, thus representing a new kind of boron-doped MRs. The boron atoms endow them with sufficient Lewis acidity, and notably, the formed Lewis acid-base adducts based on borondoped MRs display the photo-induced dual-dissociation behavior in the excited state and thus photochromism property. Moreover, despite of the highly contorted topological conformations, their potential utility as organic semiconductor was demonstrated by fabrication of organic field-effect transistors.

crystal occurs mainly due to the expansion of elementary layers of growth. They are 8.8 Å units high, which is equivalent to parameter a of a unit cell, and given the peculiarities of the specific structure, is also equivalent to one of the sizes of С 10 H 10 N 2 O 4 molecule. The statistical data processing reveals considerable differences in tangential dissolution rate on the two spirals, consisting of nine and four screw dislocations correspondingly. Right-screwing growth layers of the left spiral join, at some distance, the left-screwing steps of the right spiral, forming an even more complex source-a growth analogy of dislocational Frank-Read source. To calculate the tangential rates for such source, each image was overlaid by a special grid affixed to defined points-canals of dislocations. Then the position data of intersection points of grid meridian and the step contour were taken. Each two images required more than a thousand of coordinate readings. Then we schemed the step rate distribution for every image pair. The distribution came out to be bimodal, which required segregation of the results for the left and the right spirals. Each distribution was then approximated to the lognormal distribution, average tangential rates were determined as expectation value, and rate fluctuations were calculated as a mean-square deviation. The results show that for the left source steps the average tangential rate is two times greater than that for the right source ones throughout the whole experiment. On the whole, the tangential rate decreases towards the end of the experiment. The rate fluctuations for the steps of both groups also reveal an almost monotonous decrease. This means that the system is working towards equilibrium. The amount of substance in the solution is increasing and dissolution is going to give place to equilibrium. This brings forward an important inference: the left and the right part of the same growth source, located at a less than a micrometer distance from each other, have a different effect on the boundary layer of the solution. We have shown that the interface needs to have the horizontal concentration gradient of the substance which would provide a faster tangential rate of the left spiral at growth and a more active decrease at dissolution. The same assumption has been verified for bigger (100 mkm) hillocks.