At last, 1,10-phenanthroline-N,N-dioxide, a new type of helicene, has been synthesized using HOF · CH₃CN

For more than 50 years the synthesis of 1,10-phenanthroline-N,N'-dioxide (2) has been sought. The reason for the failure of all the earlier attempts is that the limited space in the bay area of the starting material 1,10- phenanthroline (1) cannot accommodate two oxygen atoms. The oxidation has now been achieved with the oxygen-transfer agent HOF. CH₃CN, and X-ray studies have revealed that the product is not planar but is a new type of helicene - in this way the 'space problem' for the two oxygen atoms has been solved.