Derivatives of tetraethynylethene (TEE, 3,4-diethynylhex-3-ene-1,5-diyne) and (E)-1,2-diethynylethene ((E)-DEE, (E)-hex-3-ene-1,5-diyne) provide a unique class of π-conjugated building blocks for modular construction of one- and two-dimensional carbon-rich scaffolds such as monodisperse, linearly π-conjugated oligomers extending in length beyond 10 nm or large macrocyclic all-carbon cores. Lateral functionalisation of these novel chromophores with donor–acceptor substituents strongly enhances their advanced materials properties and leads to exceptional third-order optical nonlinearities. New photochromic molecules were prepared which undergo photochemical cis → trans and trans → cis isomerisation without competing thermal isomerisation pathways, thereby paving the way for applications as light-driven molecular switches in optoelectronic devices.