inserting datetime from aspx page returns Conversion failed when converting date and/or time from character string.

dear all,
i have a code behind function whihc inserts current datetime to sql server
and following is my code
Dim reqdetails = Convert.ToDateTime(DateTime.Now).ToString("yyyy-MM-dd H:mm:ss")
   insert into tbl_1 (empname,upd_date) values  ('a', '" & reqdetails& "')
it returns following error
Conversion failed when converting date and/or time from character string.
thanks
nick