chroot: failed to run command `/bin/bash': No such file or directory

MAY BE you put the library into wrong place(/lib or /lib64). 

test environment: I test this in a linux box which run gentoo x86_64, and wanna to chroot into a directory that contain files which copy from my running system.
for short: chroot in to a x86_64 system from a x86_64 system. 
sys-apps/coreutils-8.5

commad that i used is "chroot /tmp/newroot/ /bin/bash", i'm sure i had copied the bash program and library into /tmp/newroot, why this hapen?

# tree ./
├── bin
├── lib
│   ├── ld-linux-x86-64.so.2
│   ├── libc.so.6
│   ├── libdl.so.2
│   └── libncurses.so.5
├── lib64.tar
└── lib.tar
chroot into this dir will make error as: chroot: failed to run command `/bin/bash': No such file or directory

and put all library in /lib64 will be crooect, tree ./ show this: 
├── bin
├── lib64
│   ├── ld-linux-x86-64.so.2
│   ├── libc.so.6
│   ├── libdl.so.2
│   └── libncurses.so.5
├── lib64.tar
└── lib.tar

let's test it now:
# chroot ./ /bin/bash
I have no name!@localhost /$