1.1. Background

Conjugated organic compounds play a primary role in the development of a new generation of optical and electronic materials. Molecules, oligomers, and polymers with carbon, heteroatomic, or organometallic frameworks have been widely explored as media for electroluminescence, data storage, and nonlinear optics. 1 The most intensely studied conjugated molecules with carbon-rich frameworks feature extended, linearly-conjugated π-systems. There are, however, alternative modes of π-electron communication, including cross conjugation and omniconjugation2 that can also produce electronically interesting materials. Cross-conjugated molecules are molecules with “three unsaturated groups, two of which although conjugated to a third unsaturated center are not conjugated to each other”. 3 In comparison to linearly-conjugated materials, oligomeric and polymeric compounds with a fully cross-conjugated carbon backbone are relatively unexplored. This is not to say, however, that molecules with a cross-conjugated framework are rare. 4 The situation is, in fact, quite the opposite. Cross conjugation can be found in a wide range of molecules, including such examples as quinones, radialenes, fulvalenes, and fused aromatics. It has only been recently, however, that nonaromatic cross-conjugated frameworks have emerged as a versatile platform for the synthesis of expanded cyclic and acyclic systems. As a result, trends in the structural, physical, and electronic properties of materials with a fully crossconjugated π-backbone are only now starting to reveal themselves.