NOVELTY - Bifluorenylidene derivatives and their corresponding radical anions and cations are new.    USE - In electronic devices and components, selected from organic light emitting diodes (OLEDS), organic semi-conductors, organic field-effect transistors (OFETS), molecular rectifiers, lasers; organic photovoltaic devices; organic spin valves; solar cells; electrochromic and thermochromic materials for electronic components and devices on a molecular scale; components and devices for gaseous H2 sensors; integrated circuits based on organic compounds; solar cells based on organic compounds; light-emitting transistors based on organic compounds; light-emitting electrochemical cells; organic photoreceptors and organic laser-diodes; components and devices for the production, transmission and detection of electromagnetic frequencies also in the far infra-red field; components and devices for spintronics, for chemical sensors and in general meta materials; as negative charge (electrons) or positive charge (holes) transfer materials or as guest materials in electronic devices. Also useful as active unit in photovoltaic devices and electroluminescence devices, including lasers; and as charge transfer materials in electroluminescence devices; transistors; telecom devices, i.e. for the production, transmission and detection of electromagnetic frequencies and in general for the industrial production of metamaterials. The OLEDS are devices for light-emitting diodes, in particular emitting in the visible, in the blue and the green-blue and emitting white light, in particular for television screens; and the OFETS, i.e. field-effect transistors are based on organic compounds.    DETAILED DESCRIPTION - Bifluorenylidene derivatives of formula (II), and their corresponding radical anions and cations are new.    Y'=C=O;    m= greater than or equal to 0 (preferably 1);    A'=H, OH, halo, amino, thiol, alkyl, oxyalkyl, alkenyl, alkynyl, aryl or boranyl.    Provided that: when m=0, then A' is boranyl. An INDEPENDENT CLAIM is included for the preparation of bifluorenylidene derivatives (II), and their corresponding radical anions.