Ten‐Membered Heterocyclic Diynes X‐ray Structure Analysis and PE‐Spectroscopic Investigations

X‐ray investigations on the ten‐membered heterocyclodiynes 1 – 4 reveal a chair‐like conformation for all four compounds. The triple bonds are oriented parallel to each other, the distances between them varying between 3.10 Å ( 2 ) and 2.91 Å ( 1 ). All triple bonds are slightly bent, the deviation from 180° varies between 6 – 10°. The photoelectron spectra of 1 and 3 – 6 have been recorded. The first six bands have been assigned by comparing them with related species and MO calculations. In the case of 3 – 6 , the HOMO is predicted to be a long pair combination. The splitting between the in‐plane π‐linear combinations η − i , η + i ranges from 0.9 eV ( 5 ) up to 1.5 eV ( 4 ).