[en] The three neutron-deficient nuclei ⁹⁴Pd, ⁹⁸Cd and ¹⁰⁴Sn in the vicinity of ¹⁰⁰Sn were investigated by means of in-beam γ-ray spectroscopy of excited states. The isomeric decays in ⁹⁴Pd and ⁹⁸Cd were studied for the first time with an exclusive experimental setup for delayed γ-ray detection with complete exit channel identification based on information from neutron and charged-particle filter detectors. The structure of excited states of ⁹⁴Pd showed the first indication of increasing proton-neutron interaction towards the N=Z line in this region of nuclei, that in turn might be related to increased proton-neutron pairing correlations predicted in T_z=0 nuclei. The closest neighbours of ¹⁰⁰Sn with two active particles, ⁹⁸Cd and ¹⁰²Sn, are now known with their lowest excited states. The measured reduced transition probabilities for the decay of the isomeric 8⁺ and 6⁺ states in ⁹⁸Cd and ¹⁰²Sn, respectively, allowed to extract an effective quadrupole charge for neutron and proton in this region of nuclei based on the high configurational purity of the states. While the neutron effective charge appeared to be large and in agreement with expectation, the proton effective charge value is very small (e_π≤1). This controversial result, which would indicate that ¹⁰⁰Sn is a very good closed shell nucleus with respect to quadrupole excitation, is not understood. An experimental reason for this result, related to existence of a core excited isomer, observed in the experiment by means of its half life but not γ-rays, which may have escaped observation, can not be definitely excluded and is left as possible explanation. (orig.)