Unicode Chars With Like Query Statement Problem

I have a Users table which contains a nvarchar column LastName. The
first query below returns me all the records with LastName containing
"opez" or "ópez" in them. But the second query returns only records
with "lopez" in the lastname and not records that contain "lópez".
Can anyone please tell me what is it that i am missing?

SELECT *
FROM tbUsers
WHERE (LastName LIKE '%[oó]pez%')

SELECT *
FROM tbUsers
WHERE (LastName like '%l[oó]pez%')

thanks