Spiro-based diamond-type nanogrids (DGs) two ways: 'AB'/'A + B' type gridization of vertical spiro-based fluorenol synthons.

Regular or well-defined nanogrids with atomically precise extension sites offer an opportunity for covalent nano-architectures as well as frameworks. Previously, we discovered organic nanogrids based on the 2,7-linkage of fluorene Friedel-Crafts gridization. However, the regularity of nanogrids is not always based on the actual molecular backbone, which leads to ineffective linkage for the more regular complex nanogrids such as nano-windows. Herein, we report the introduction of spirobifluorene, which has more orthogonal shapes, to fix the backbone of nanogridons with regards to the diarylfluorenes. The diamond-type nanogridons (DGs) obtained as a result have the potential feature of cross extension, which is different from their ladder-type counterparts, although they both have four well-defined extension sites. In order to screen efficient monogridon modules, we designed two types of DGs (spiro[fluorene-9,8'-indeno[2,1-]thiophene] (SFIT)-based DGs-1 and spirobifluorene-based DGs-2) and compared their synthetic routes. The results show that the Friedel-Crafts (F-C) gridization of the AB synthon (AB mode) offers DGs-1 in 44-50% yields, while the F-C gridization of A + B synthons (A + B mode) is more efficient and gives DGs-2 in 64% yield. Furthermore, unlike in the AB mode, the dehydroxylated byproduct and linear polymers were not observed in the A + B mode.