Dedicated to Professor Yitzhak Apeloig on the occasion of his 65th birthdayCircular dichroism (CD) spectroscopy can be regarded as one of the most powerful techniques for stereochemical analysis: it is sensitive to the absolute configuration as well as to conformational features, which are often completely obscured in ordinary absorption spectra.[1] The analysis of CD spectra within the exciton coupling framework is extremely useful in a number of situations.[2] Nevertheless, when a molecule contains three or more different excitonically coupled chromophores with several transitions, the resulting CD spectrum is rather complicated due to the overlap of several exciton couplets. In such cases, full CD calculations using quantum-mechanical methods are necessary, and comparison with the experimental spectra is more reliable than just considering the CD signals arising from all possible pairwise terms.[3] Furthermore, one may want to explore the CD spectra as a source of more complex information, such as the assignment of Cotton effects to specific transitions, determination of absolute configuration (AC), and even investigation of conformational preferences. Typically, a conformational analysis is performed and further evaluated by the Boltzmann equation to ascertain the relative population of all the conformers.[3] For systems with conformational stability, it is possible to deduce the preferred conformation in solution by comparing the calculated CD spectrum of the representative conformer with the experimental one.We have been involved in the preparation of ethynylated allenes [4] as building blocks for the construction of linear [5] and macrocyclic [6] carbon-rich scaffolds through oxidative acetylenic coupling. Following the synthesis of a first series of stable 1,3-diethynylallenes (DEAs), we proceeded with the preparation of shape-persistent macrocycles with allenoacetylenic carbon backbones.[6] Although DEAs are axially chiral, racemic mixtures were previously used in our group for acetylenic scaffolding. Recently, we reported the synthesis of nearly enantiopure DEA (M)-1 in 69 % yield with an enantiomer ratio (e.r.) of 96:4 by a Pd-mediated syn-S N 2'-type cross-coupling of 3-methyl-1-butyn-3-ol with an optically pure bispropargylic ester (Figure 1). [7] Full optical purity was achieved by subsequent HPLC separation. We showed that 4-N,N-dimethylanilino (DMA) donor-substituted optically active DEAs react in a facile [2 + 2] cycloaddition with tetracyanoethene (TCNE) to form, after retro-electrocyclization, optically active, photostable 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) [8] derivatives. Interestingly, CD spectroscopy revealed a chiral induction from the chiral allene moiety into the sterically crowded TCBD chromophores.Herein, we report time-dependent density functional theory (TDDFT) [9] as well as p-electron dipole velocity molecular orbital (SCF-CI-DV MO) [10] calculations to predict UV/Vis and CD spectra of 1,3-diethynylallene (DEA) (M)-2 (Figure 1). The exciton couplet in allene (M)-2 is in agre...