Polyoxometalates　(POMs)　are　an　important　class　of　metal-oxygen　clusters,　which　are　composed　of　cluster　anions　bridged　by　pre-transition　metals　(VⅤ,　NbⅤ,　TaⅤ,　MoⅥ,　MoⅤ　and　WⅥ)　and　oxygen.　On　the　basis　of　previous　studies　(H2en)2{SiW11O39Sm(H2O)2}•(H3O)•6H2O,　we　changed　rare　earth　salts　and　successfully　synthesized　three　isomorphic　crystals　(H2en)2{SiW11O39Ln(H2O)2}•(H3O)•6H2O[Ln=Ce(1),　Pr(2),　Nd(3)],　X-ray　single　crystal　diffraction　experiment　measured　that　the　four　belong　to　the　triclinic　system,　the　P1　space　group,　and　the　unit　cell　parameters　are　consistent,　indicating　that　they　have　the　same　crystal　structure.　XRD　experiments　show　that　they　have　the　same　peaks,　indicating　that　the　substances　are　identical.　Due　to　the　same　cluster　anions　and　only　the　substituted　rare　earth　ions　are　different,　these　isomorphic　crystals　exhibit　similar　phenomena　in　many　characterization　methods,　for　example　the　similar　absorption　curves　in　1D　infrared　spectroscopy:　the　vibrational　absorption　of　anion　skeleton　belonging　to　Keggin　cluster　appears　at　1　039,　949,　889　and　787　cm-1,　and　the　absorption　peaks　of　νas(O-H)　and　δ(O-H)　occur　in　the　vicinity　of　3　600~3　300　and　1　600~1　630　cm-1.　The　stretching　vibration　peaks　of　N-H　and　C-H　ligands　of　ethylenediamine　were　observed　in　3　277,　2　927　and　2　855　cm-1.　However,　the　two-dimensional　infrared　correlation　spectra　under　magnetic　perturbation　are　sensitive　to　the　magnetic　field　response.　The　two-dimensional　infrared　correlation　spectra　under　thermal　perturbation　are　easy　to　capture　the　subtle　changes　of　hydrogen　bond　vibration　modes.　Therefore,　two-dimensional　infrared　spectroscopy　can　be　used　for　fine　determination　of　molecular　structure,　and　the　comparative　analysis　of　two-dimensional　infrared　spectroscopy　of　such　isomorphic　polyoxotungstate　has　not　been　reported.　Two-dimensional　infrared　correlation　spectra　under　magnetic　perturbation　show　that　compound　1　has　response　peaks　at　468,　560　and　810　cm-1,　which　belong　to　νas(Ln-O),　skeleton　ν(W-O)　and　νas(W-Ob),　respectively.　Compound　2　exhibits　as　(Ln-O)　at　450,　464,　475　cm-1,　and　the　response　peak　at　570,　675　cm-1　belongs　to　skeleton　ν(W-O).　The　response　peaks　of　compound　3　at　452,　468,　472　cm-1　belong　to　νas　(Ln-O),　and　518,　533,　545,　565,　695　cm-1　belong　to　skeleton　ν(W-O).　The　number　of　response　peaks　of　compound　1,　2,　3　belongs　to　skeleton　ν(W-O)　increases.　This　is　due　to　the　valence　electron　configurations　of　Ce3+,　Pr3+,　Nd3+　are　4f1,　4f2,　4f3.　The　valence　electron　number　increases,　so　the　influence　of　magnetic　particle　Ln3+　on　adjacent　W-O　bonds　increases.　Two-dimensional　infrared　correlation　spectra　under　thermal　perturbation　show　that　compounds　1,　2　and　3　have　as　(Ln-O)　response　peaks　at　about　400　cm-1,　and　the　response　peaks　of　νas　(W-Ob)　and　νas　(W-Od)　appear　at　810,　860　and　940　cm-1,　which　are　due　to　the　same　cluster　skeleton　and　the　same　hydrogen　bond.　However,　the　most　strong　peak　positions　of　νas　(W-O)　belong　to　compounds　1,　2,　3　appear　at　810,　850,　855　cm-1,　which　may　because　the　different　polarities　of　Ln　ions　substituted　on　cluster　skeletons　have　different　effects　on　the　dipole　moments　of　adjacent　W-O　bonds.　The　similarities　and　differences　of　these　isomorphic　rare　earth　substituted　polyoxotungstate　can　be　well　analyzed　by　two-dimensional　infrared　spectroscopy.　©　2020,　Peking　University　Press.　All　right　reserved.