A breathtaking game seemed to be going the way of the Spanish visitorâ€™s who dominated for long periods, particularly in the first half when only a string of Manuel Almunia saves denied them.
The game reached half time scoreless much to the relief of the Gunners team who found themselves chasing the game for much of the half.
If Almunia had kept Arsenal in the game the Spanish stopper was at fault within a minute of the restart.
The hosts defence allowed Zlatan Ibrahimovic a clear run on goal and with the keeper in no-mans land a cool lob opened the scoring.
Arsenal had not learned their lesson and on 59 minutes Xavi released Ibrahimovic again and this time the sheer power of the shot defeated Almunia.
But the home side were given a lifeline back into the game on 69 minutes courtesy of substitute Theo Walcott who raced into the area and fired under Victor Valdes.
With six minutes remaining the fightback was complete as Carles Puyol bundled over Reds skipper Cesc Fabregas as he prepared to shoot and was shown a straight red.
Fabregas drove the resulting penalty straight down the middle of goal to complete a rousing second half and give the Gunners a glimmer of hope for the second leg next week.
As for Barcelona they will be disappointed they did not book their semi-final pace tonight after being in command for so long.
Walcott told ITV1 â€œIt was good game for the neutral and to play in.
â€œI knew that if things werenâ€™t going too well Iâ€™d get a chance to come on and show what I could do.
â€œWe were very disappointed with the two goals as you want to keep clean sheets, but if you look back on the game they had a lot of possession and in the end 2-2 was a fair result.