No, your deduction will be for the year you pay the property taxes, 2018, even if they were your assessed property taxes for 2017.
Deducting Prior Year or Future Year Property Taxes
You can deduct prior year or future year property taxes during the year you make the actual payment – in certain situations. More info
https://ttlc.intuit.com/questions/1899887-can-i-deduct-property-real-estate-taxess. More info
