Problem connecting an early 2009 iMac running OS X El Capitan to a late 2013 iMac running MacOS Catalina with a MiniDisplay port to MiniDisplay port cable.

I'm trying to use an early 2009 iMac running OS X El Capitan to use as a target display from a late 2013 iMac running OS X Catalina. The first one has a mini display port and the second one a thunderbolt 1 port.

I have tried 2 different cables mini diplay port to mini display port and nothing happens when I press cmd+F2 command.

Could someone tell me why?