The Gunners have already agreed a deal with Bundesliga outfit Borussia Dortmund for Sokratis Papastathopoulos, and the defender's contract is due to be announced on 1st July, but Arsenal are not done yet.
They are targeting Martins, who has opted to terminate his contract with Sporting Lisbon, after several players were violently attacked at the club training ground last month.
The winger could be available therefore, on a free transfer and Arsenal are hoping to pounce. The 23-year-old managed to score 10 goals from 42 appearances in the Portuguese top-flight last campaign.
As for Leno, the Leverkusen goalkeeper has tallied up 304 appearances for the Bundesliga club, but has been informed that he can leave after they signed Eintracht Frankfurt's Lukas Hradecky.
Arsenal are seeking out a new goalkeeper to replace Petr Cech on a long-term basis, and Leno fits the bill. He was named in Germany's provisional World Cup squad, but was omitted from the final 23.