Shape-persistent macrocyclic diene and diyne, which consist of two quaterphenyl units, were synthesized by McMurry coupling of 5,5 0 -bis(3-formylphenyl)-2,2 0 -dimethoxybiphenyl as a key step. The macrocycles have achiral (meso) and chiral (racemic) conformational isomers owing to two asymmetric axes of the biaryl units. According to the theoretical calculations, the chiral conformers are about 1 kcal mol À1 lower than the corresponding achiral conformers in energy. The NMR spectra indicate that the interconversion between the diastereomers occurs with relatively low energy barrier (<10 kcal mol À1 ). An X-ray crystallographic analysis of the diyne reveals that it has a double-helically twisted chiral structure and low strain nature of the molecule as expected. Moreover, the molecules construct a layered structure with channels that are filled with two chloroform molecules. Potential utilities such as a chiral sensor were also investigated. To cite this article: T.

The synthesis of phenalenyl-endcapped [5]cumulene as acumulene-based singlet biradical and the spin correlation changes of one-dimensional aggregates are described. The high propensity for self-aggregation of phenalenyl rings and the introduction of bulkys ubstituents into the appropriate positions led to the formation of aone-dimensional chain assembly. Single-crystal X-ray structural analysis indicated that the bond length alternation of the cumulene chain increased with decreasing temperature,a long with improved overlapping of the phenalenyl rings.V ariable-temperature Raman spectroscopy and magnetic susceptibility measurements revealed that al ocalized spin pair within the molecule decouples at low temperatures,a nd ac ontinuum spin system involving intraand intermolecular spin-spin interactions emerges in the onedimensional chain.Scheme 1. Phenalenyl-and fluorenyl-endcapped cumulenes.

The synthesis of phenalenyl‐endcapped [5]cumulene as a cumulene‐based singlet biradical and the spin correlation changes of one‐dimensional aggregates are described. The high propensity for self‐aggregation of phenalenyl rings and the introduction of bulky substituents into the appropriate positions led to the formation of a one‐dimensional chain assembly. Single‐crystal X‐ray structural analysis indicated that the bond length alternation of the cumulene chain increased with decreasing temperature, along with improved overlapping of the phenalenyl rings. Variable‐temperature Raman spectroscopy and magnetic susceptibility measurements revealed that a localized spin pair within the molecule decouples at low temperatures, and a continuum spin system involving intra‐ and intermolecular spin–spin interactions emerges in the one‐dimensional chain.