Question

Can I get an explanation on how NO in brown ring complex possess a +1 charge?

Answer 1

Brown ring is a complex of the formula : [Fe(H2O)5NO]SO4

Initially FeSO4 in aqueous solution exist as [Fe(H2O)6]SO4 , here oxidation number of Iron is +2, that is Fe (II).
Now NO is added
[Fe(H2O)6]SO4 + NO --> [Fe(H2O)5NO]SO4
However a charge (electron) transfer from the NO Nitrosyl ligand to the Iron occurs making the oxidation state( charge) of NO as +1 and reducing the Iron from Fe (II) to Fe (I).

Therefore NO possess a charge of +1.