escaping - Grep invalid reference for Escape character -

i trying execute following command

var1="/home/backup.sh -f /home/conf -d 1 >> /home/backup_date +"\%d\%b\%y".log 2>&1" var2="xxxxxx"

grep "$var1" "$var2" flashing invalid reference.

it works if remove escape character before %. need adding command cronjob upon condition check , getting invalid reference error grep.