Brentford have signed Portugal under-21 striker Alberto Coelho from Sporting Lisbon on a season-long loan.
Transfer news: Jermain Defoe unlikely to return to Premier League after interest from QPR and Leicester
Jermain Defoe is unlikely to join Queens Park Rangers on deadline day, according to chairman Tony Fernandes.
The Cottagers revealed the move for the 21-year-old on their official Twitter feed, with Frimpong also acknowledging it by writing: "Fulham here I come".
Frimpong has been with Arsenal since he was nine but did not make his Premier League debut until August 2011 after a succession of injuries.
Fitness problems also cut short a loan spell with Wolves last season, with Frimpong needing surgery after rupturing knee ligaments against QPR.
He went on loan to Charlton at the end of 2012 and will now see out the season with Martin Jol's men.