The 25-year spent last season on loan at Italian champions Juventus, but he struggled to make his mark in Serie A after failing to find the net in his nine league appearances.
Arsenal are prepared to allow the Denmark international to leave the Emirates Stadium, with reports suggesting they have lowered their asking price to around £3million.
The striker made the move to London in 2005 but he has been unsuccessful in his bid to hold down a regular place in Arsene Wenger's side.
Frankfurt's Bundesliga rivals Borussia Monchengladbach rejected suggestions that they were chasing Bendtner earlier in the summer and he could now line up against them next season.
Bendtner had been linked with moves to Malaga and Hamburg, amongst other European clubs, but Buchhagen says that Frankfurt are in discussions with the Dane.
"We are in serious negotiations with Bendtner," he told BT.
Frankfurt had been reported to have been chasing Sparta Prague striker Vaclav Kadlec, but their pursuit of Bendtner could mean the move is now on standby, as Buchhagen denied that any deal has been done.
"Kadlec is not bought yet," he added.