help: IFS in /bin/sh

i've ben trying to make something work but still havent figured something out.
I do the following:
[user@host ~]$ IFS=/
[user@host ~]$ export IFS
[user@host ~]$ PATH=.:$PATH
[user@host ~]$ echo "/bin/sh" > bin
[user@host ~]$ chmod 755 bin

Now the problem is:
if I execute 'sh -c "/bin/ls"' it just does a simple ls
But if i do 'sh -c "sh -c \"/bin/ls\""' it does what i expected (it executes the file 'bin')

Why doesn't it does the same in the first example??

thank's for your spent time.

You don't need the quotes...

Yes i know that gives me the list of files in the directory, but what i was expecting is to execute with that very same command line the program bin,due to my configuration of my IFS in sh.