Gas-phase rotational spectroscopy of AlCCH (X∼1Σ+): A model system for organo-aluminum compounds

► Pure rotational spectrum of AlCCH measured using FTMW and millimeter spectroscopy. ► Accurate structure for AlCCH was determined from measurements of five isotopologues. ► AlCCH has an acetylenic structure with little modification of C-C triple bond. ► Quadrupole constant measured for aluminum indicates a chiefly covalent Al-C bond.