© The Royal Society of Chemistry and Owner Societies. Ultrafast reversible DNA/RNA photo-cross-linking is a powerful tool for regulating the target strand in living cells. In particular, 3-cyanovinylcarbazole (CNVK) and 3-cyanovinylcarbazole modified by d-threoninol (CNVD) can photo-cross-link to pyrimidine bases within a few seconds of photoirradiation. However, these photo-cross-linkers can only cross-link to the counter base if it is adjacent to the 5′-side (-1 position). In this study, we synthesized novel photo-cross-linkers with varying linker lengths capable of photo-cross-linking with pyrimidine bases at locations other than the-1 position via click chemistry. The photo-cross-linking site was dependent on linker length. This journal is