Is it obligatory to pay Zakat on a bank account that reached the nisab in the eleventh or twelfth month of last year, given the doubt concerning the ruling on dealing with banks in Turkey, which some consider usurious?

If you are unsure about the time when the nisab (definition) (minimum threshold for zakat (definition)) was reached, then zakat is not obligatory upon you until you are certain that a hawl (lunar year) has passed after the nisab was reached. The default is that your liability is absolved. However, if you pay it despite the doubt, it is good and more cautious. As for banks, you can ascertain the permissibility of their transactions by inquiring about them. If it becomes clear that they are usurious, then dealing with them is forbidden. If doubt persists, it is more cautious to avoid them, based on the saying of the Prophet (peace be upon him): "Whoever guards himself against doubtful matters, he has indeed guarded his religion and his honor."