Compositions and methods of preparing carboranes and metallacarboranes, which can be used as a new type of electrochemically active label for biological compounds, are disclosed. Nucleic acid derivatives labelled with carborane or metallacarborane can be detected by electrochemical methods and can find several practical applications, such as materials for nanoconstruction, in DNA array technology or for the construction of biosensors, especially electrochemical biosensors. Other applications can include use as modified primers in amplification of RNA and DNA, antisense drugs, boron carriers for BNCT, radiopharmaceuticals bearing a range of isotopes useful in different types of radiotherapy, molecular probes, elements of biosensors, materials for nanotechnology and others.