In this case: 
I've seen this similar in other games (in game; if you wanted to PM [ie. clan members/single person]) you could type something like: 
/m  
ie: /m XJC hey what's up? 
- and it would send it to all members with XJC in their name with the message "hey what's up?" - seen in games like RtCW: Enemy Territory.  That's a workaround from Alt+Tabbing to another chat client.