| abstract |
The invention relates to spiro compounds of the general formula (I) wherein X?1, X2, X3, and X4¿ are the same or different and are -S-, -O-, -NR?5-, -CR5¿=N- or -CR5=CH- on the condition that at least one of the groups X1-4 is different from -CR5=CH-. Said spiro compounds are suitable for use as charge transfer materials, especially for photovoltaic cells, and as electroluminescence materials. |