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organic compounds
Cyclobutaarenes are highly strained compounds which exhibit unusual geometric features. Introduction of diphenyl substituents on the peripheral C atoms of the cyclobutene ring adds stereoelectronic effects and causes further distortion of the ring structure. The interatomic distances observed for the peripheral C-C bonds in the cyclobutene moiety of the two compounds are in the range 1.71-1.72Å, among the longest of Csp3-Csp3 bonds previously reported for similar compounds. The core structure of the phenanthrodicyclobutene derivative is severely twisted due to non-bonding interactions between the chlorine substituents.