Answer:
It's a covalent bond
Explanation:
The diference of electronegativity between the two atoms bonding can help you to decide if a bond is either covalent or ionic.
As shown in the figure, the oxygen atoms of the nitrate (left) will interact with the nitrogen atom of the thiamine(right).
The oxygen have an electronegativity of 3.5 (one of the most electronegative elements) and the nitrogen a 3.0
Being the difference: 3.5 - 3.0=0.5
Now, how this helps to decide the type of bond? For covalent bonds it's expected to have a electronegativity diffetence of < 1.5. On the other hand, for ionic bonds this value should be > 1.5
