.net Frameworks compatibility

I Create A new application in the framework 4.5 and i have an older application was created in 1.1 framework , i want to call a form that exist in the new application from the old one . i already try to load The executable application file using the assembly class , Assembly.loadfrom() that i used before and works fine between 2 different application, that have same frameworks , Now an exception was thrown that the Assembly is invalid the question is it's possible to call an new Assembly from an older one thank you